Fluorine-containing ether compound, lubricant for magnetic recording medium, and magnetic recording medium

Abstract

A fluoroether compound represented by the formula R1-CH2- R2-CH2- R3-CH2-R4-CH2-R5-CH2-R6-CH2-R7 (where R2, R4, and R6 are each a perfluoropolyether chain, R3 is formula (2), R5 is formula (3), and R1 and R7 are each independently a terminal group including two or three polar groups, wherein the polar groups have been bonded respectively to different carbon atoms and the carbon atoms having the polar groups bonded thereto have been bonded to each other by a linking group including a carbon atom having no polar group bonded thereto).

Description

[Technical Field]

[0001] The present invention relates to a fluorine-containing ether compound, a lubricant for a magnetic recording medium, and a magnetic recording medium. This application claims priority based on Japanese Patent Application No. 2021-065869, filed on April 8, 2021, the contents of which are incorporated herein by reference. [Background technology]

[0002] In order to increase the recording density in magnetic recording and reproducing devices, development of magnetic recording media suitable for high recording densities is underway. Conventional magnetic recording media include those in which a recording layer is formed on a substrate and a protective layer made of carbon or the like is formed on the recording layer. The protective layer protects the information recorded on the recording layer and improves the sliding properties of the magnetic head. The protective layer also covers the recording layer to prevent the metal contained in the recording layer from being corroded by environmental substances.

[0003] However, the durability of a magnetic recording medium cannot be sufficiently achieved by simply providing a protective layer on the recording layer. Therefore, a lubricant is applied to the surface of the protective layer to form a lubricating layer with a thickness of approximately 0.5 to 3 nm. The lubricating layer improves the durability and protective power of the protective layer and prevents contaminants from penetrating into the magnetic recording medium. After forming the lubricating layer on the surface of the protective layer, a burnishing process may be carried out to remove protrusions and particles present on the surface of the magnetic recording medium and to improve the smoothness of the surface.

[0004] Lubricants used in forming the lubricating layer of a magnetic recording medium include, for example, those containing a fluorine-based polymer having a repeating structure containing -CF2- and having polar groups such as hydroxyl groups at the terminals. For example, Patent Document 1 discloses a magnetic disk provided with a lubricating layer containing a fluorine-containing ether compound that contains three perfluoropolyether chains in the molecule and has the same structure at both ends. Patent Document 2 discloses a magnetic disk provided with a lubricating layer containing a fluorine-containing ether compound that contains three perfluoropolyether chains in the molecule and has two terminal structures that are different from each other. Patent Document 3 also discloses a magnetic disk having a lubricating layer containing a lubricant that contains three perfluoropolyether chains in the molecule and the linking groups between the perfluoropolyether chains have two hydroxyl groups. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 116742 [Patent Document 2] International Publication No. 2017 / 145995 [Patent Document 3] US Patent Application Publication No. 2016 / 0260452 Summary of the Invention [Problem to be solved by the invention]

[0006] In magnetic recording and reproducing devices, there is a demand for an even smaller flying height of the magnetic head, which in turn requires a thinner lubricating layer in the magnetic recording medium. However, when the thickness of the lubricating layer is reduced, the corrosion resistance of the magnetic recording medium may become insufficient. In particular, when a tape burnishing process is performed on the surface of the magnetic recording medium after the lubricating layer is formed, the corrosion resistance of the magnetic recording medium tends to become insufficient. For this reason, a lubricating layer that is highly effective in suppressing corrosion of the magnetic recording medium is required.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluorine-containing ether compound suitable as a material for a lubricant for a magnetic recording medium, which can form a lubricating layer having a high corrosion-inhibiting effect on the magnetic recording medium. Another object of the present invention is to provide a lubricant for magnetic recording media, which contains the fluorine-containing ether compound of the present invention and is capable of forming a lubricating layer that has a high corrosion-inhibiting effect on magnetic recording media. Another object of the present invention is to provide a magnetic recording medium having a lubricating layer containing the fluorine-containing ether compound of the present invention and having excellent corrosion resistance. [Means for solving the problem]

[0008] That is, the present invention relates to the following items. A first aspect of the present invention provides the following fluorine-containing ether compound: [1] A fluorine-containing ether compound represented by the following formula (1): R 1 -CH2-R 2 -CH2-R 3 -CH2-R 4 -CH2-R 5 -CH2-R 6 -CH2-R 7 (1) (In formula (1), R 2 , R 4 and R 6 are the same or different perfluoropolyether chains; R 3 is a linking group represented by the following formula (2); R 5 is a linking group represented by the following formula (3); R 1 and R 7 are terminal groups each independently containing two or three polar groups, each polar group being bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded being bonded via a linking group containing a carbon atom to which no polar group is bonded.

[0009] [ka] (In formula (2), a is an integer of 1 to 3, and b is an integer of 1 or 2; in formula (3), c is an integer of 1 to 3, and d is an integer of 1 or 2; however, a in formula (2) and c in formula (3) cannot be 1 at the same time.)

[0010] The fluorine-containing ether compound of the first aspect of the present invention preferably has the characteristics described in the following [2] to [8]. It is also preferable to arbitrarily combine two or more of the characteristics described in the following [2] to [8]. [2] The fluorine-containing ether compound according to [1], wherein a in the formula (2) is an integer of 2 or 3, and c in the formula (3) is an integer of 2 or 3. [3] In the formula (1), R 1 and R 7 The fluorine-containing ether compound according to [1] or [2], wherein all of the polar groups are hydroxyl groups.

[0011] [4] In the formula (1), -R 1 and -R 7 are each independently a terminal group represented by the following formulas (4-1) to (4-5):

[0012] [ka] (In formula (4-1), e is an integer of 0 to 1, and f is an integer of 1 to 4.) (In formula (4-2), g is an integer of 1 to 2, and h is an integer of 1 to 3.) (In formula (4-3), i is an integer of 1 to 3.) (In formula (4-4), j is an integer of 1 or 2.)

[0013] [5] R in the formula (1) 2 , R 4 , R 6 Each of the following formulas (5) to (9) is independently any one of the following formulas (5) to (9): -CF2O-(CF2CF2O) k -(CF2O) l -CF2- (5) (In formula (5), k and l each represent an average degree of polymerization, and each represents 0.1 to 20.) -CF2O-(CF2CF2O) m -CF2- (6) (In formula (6), m represents the average degree of polymerization and represents 0.1 to 20.) -CF2CF2O-(CF2CF2CF2O) n -CF2CF2- (7) (In formula (7), n represents the average degree of polymerization and represents 0.1 to 20.) -CF2CF2CF2O-(CF2CF2CF2CF2O) o -CF2CF2CF2- (8) (In formula (8), o represents the average degree of polymerization and represents 0.1 to 10.) -CF(CF3)O-(CF2CF(CF3)O) p -CF(CF3)- (9) (In formula (9), p represents the average degree of polymerization and is 0.1 to 20.)

[0014] [6] In the formula (1), R 1 and R 7 The fluorine-containing ether compound according to any one of [1] to [5], wherein [7] In the formula (1), R 2 and R 6 The fluorine-containing ether compound according to any one of [1] to [6], wherein [8] The fluorinated ether compound according to any one of [1] to [7], which has a number average molecular weight in the range of 500 to 10,000.

[0015] A second aspect of the present invention provides the following lubricant for a magnetic recording medium. [9] A lubricant for magnetic recording media, comprising the fluorine-containing ether compound according to any one of [1] to [8]. A third aspect of the present invention provides the following magnetic recording medium.

[10] A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, A magnetic recording medium, wherein the lubricating layer contains the fluorine-containing ether compound according to any one of [1] to [8]. The magnetic recording medium according to the third aspect of the present invention preferably has the characteristics described in

[11] below.

[11] The magnetic recording medium according to

[10] , wherein the lubricating layer has an average film thickness of 0.5 nm to 2.0 nm. [Effects of the Invention]

[0016] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and therefore can be used as a material for a lubricant for magnetic recording media, which can form a lubricating layer that has a high corrosion-inhibiting effect on magnetic recording media. The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore can form a lubricating layer that has a high corrosion-inhibiting effect on magnetic recording media. The magnetic recording medium of the present invention has a lubricating layer containing the fluorine-containing ether compound of the present invention, and therefore has excellent corrosion resistance. Therefore, the magnetic recording medium of the present invention has excellent reliability and durability. Furthermore, the magnetic recording medium of the present invention has a lubricating layer that has a high corrosion suppression effect on the magnetic recording medium, and therefore the thickness of the protective layer and / or lubricating layer can be reduced. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic cross-sectional view showing an example of an embodiment of a magnetic recording medium of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] In order to solve the above problems, the present inventors have conducted extensive research, focusing on the chain skeleton and terminal groups of fluorine-containing ether compounds. As a result, they found that a fluorine-containing ether compound having a chain structure consisting of a methylene group (-CH2-) and an ether bond (-O-), to which three perfluoropolyether chains are linked by two specific linking groups, each of which has one or more hydroxyl groups bonded, and in which specific terminal groups containing two or three polar groups are bonded to both ends of the chain structure via a methylene group, would be sufficient.

[0019] In the fluorine-containing ether compound having the chain skeleton, one or both of the two linking groups have a methylene chain having 2 or 3 carbon atoms between the central perfluoropolyether chain and the carbon atom to which the hydroxyl group is bonded. This is presumed to result in a lubricating layer containing the fluorine-containing ether compound having the chain skeleton having appropriate hydrophobicity.

[0020] In addition, when the lubricating layer that contains the fluorine-containing ether compound with the chain skeleton described above is formed on the protective layer, both ends of the perfluoropolyether chain that is located at the center of the chain skeleton are adhered to the protective layer by the hydroxyl group of the linking group that is located between the perfluoropolyether chains.Therefore, the lubricant that contains the fluorine-containing ether compound with the chain skeleton described above has one or two perfluoropolyether chains, and compared with the case that contains the fluorine-containing ether compound that has the same number of carbon atoms as the chain skeleton described above, it is easy to wet and spread on the protective layer, can adhere uniformly to the protective layer, and can form a lubricating layer with high coverage and good adhesion.

[0021] Moreover, at both ends of the chain skeleton, each independently contains two or three polar groups, each polar group being bonded to a different carbon atom, and the carbon atoms bonded to the polar groups are bonded to each other via a linking group containing a carbon atom not bonded to the polar group, and an end group is arranged in which the carbon atoms bonded to the polar groups are bonded to each other.The two or three polar groups of this end group can be oriented to be able to adhere to the protective layer, unlike the end group in which the carbon atoms bonded to the polar groups are bonded to each other.Therefore, compared to the lubricating layer containing a fluorine-containing ether compound having an end group in which the carbon atoms bonded to the polar groups are bonded to each other, it is possible to form a lubricating layer with high coverage and good adhesion.Furthermore, since the end group has a linking group containing a carbon atom not bonded to the polar group, the hydrophobicity is improved compared to the lubricating layer containing a fluorine-containing ether compound having an end group in which the carbon atoms bonded to the polar groups are bonded to each other.

[0022] Thus, a lubricating layer containing a fluorine-containing ether compound having the specific terminal groups bonded to both ends of the chain skeleton has appropriate hydrophobicity and good adhesion to a protective layer, and is therefore presumed to have a high corrosion-inhibiting effect on magnetic recording media. The present inventors conducted further studies and found that forming a lubricating layer containing the above-mentioned fluorine-containing ether compound on a protective layer had a high corrosion-inhibiting effect on the magnetic recording medium, leading to the invention.

[0023] Preferred examples of the fluorine-containing ether compound, lubricant for magnetic recording media (hereinafter sometimes abbreviated as "lubricant"), and magnetic recording media of the present invention will be described in detail below. The present invention is not limited to the following embodiments. The number, amount, position, ratio, material, configuration, etc. of the present invention can be added, omitted, substituted, or changed within the scope of the present invention.

[0024] [Fluorine-containing ether compounds] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1). R 1 -CH2-R 2 -CH2-R3 -CH2-R 4 -CH2-R 5 -CH2-R 6 -CH2-R 7 (1) (In formula (1), R 2 , R 4 and R 6 are the same or different perfluoropolyether chains; R 3 is a linking group represented by the following formula (2); R 5 is a linking group represented by the following formula (3); R 1 and R 7 are terminal groups each independently containing two or three polar groups, each polar group bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded are bonded via a linking group containing a carbon atom to which no polar group is bonded.

[0025] [ka] (In formula (2), a is an integer of 1 to 3, and b is an integer of 1 or 2; in formula (3), c is an integer of 1 to 3, and d is an integer of 1 or 2; however, a in formula (2) and c in formula (3) cannot be 1 at the same time.)

[0026] (R 1 and R 7 ) In the fluorine-containing ether compound represented by the above formula (1), R 1 and R 7 are terminal groups each independently containing two or three polar groups, each polar group being bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded being bonded via a linking group containing a carbon atom to which no polar group is bonded. In the fluorine-containing ether compound represented by formula (1), R 1 and R 7 Each of these has two or three polar groups. Therefore, when a lubricating layer is formed on a protective layer using a lubricant containing these, a favorable interaction occurs between the lubricating layer and the protective layer.

[0027] Examples of polar groups include a hydroxyl group (-OH), an amino group (-NH), a carboxyl group (-COOH), an aldehyde group (-COH), a carbonyl group (-CO-), and a sulfo group (-SOH). 1 and / or R 7 preferably contains a hydroxyl group as a polar group, and R 1 and R 7 It is more preferable that all of the polar groups contained in R are hydroxyl groups. 1 and / or R 7 When the compound is a fluorine-containing ether compound having a hydroxyl group, when a lubricating layer is formed on a protective layer using a lubricant containing this compound, a more favorable interaction occurs between the lubricating layer and the protective layer.

[0028] In the fluorine-containing ether compound represented by formula (1), R 1 and the polar groups contained in R 7 The total number of polar groups contained in is 4 to 6. Since the total number is 4 or more, the lubricating layer containing the fluorine-containing ether compound has high adhesion (tight adhesion) to the protective layer. Furthermore, since the total number is 6 or less, in a magnetic recording medium having a lubricating layer containing a fluorine-containing ether compound, it is possible to prevent pickup of the fluorine-containing ether compound, which is too high in polarity and adheres to the magnetic head as foreign matter (smear).

[0029] R 1 and the number of polar groups in R 7 The number of polar groups contained in R is preferably the same. 1 and R 7 each containing two polar groups, or R 1 and R 7 Each of R preferably contains three polar groups. In this case, the lubricant containing the fluorine-containing ether compound adheres to the protective layer in a well-balanced manner, which makes it easier to obtain a lubricating layer with a high coverage and a high corrosion-inhibiting effect on the magnetic recording medium. In particular, R 1 and R 7When each of the compounds contains three polar groups, the polar groups contained in the fluorine-containing ether compound adhere strongly to the protective layer, resulting in a high coverage rate and a high corrosion inhibition effect on the magnetic recording medium.

[0030] R 1 and R 7 Each polar group in R is bonded to a different carbon atom. 1 and R 7 In the formula (1), the carbon atoms bonded to polar groups are bonded together via a linking group containing a carbon atom that is not bonded to polar groups.Therefore, the fluorine-containing ether compound represented by formula (1) has better hydrophobicity than, for example, a compound having an end group in which the carbon atoms bonded to polar groups are bonded together.As a result, it is estimated that the lubricating layer containing the fluorine-containing ether compound represented by formula (1) can prevent water penetration and effectively suppress the corrosion of magnetic recording medium.

[0031] In addition, when the carbon atoms that polar groups are bonded to each other are bonded through the linking group that contains the carbon atoms that polar groups are not bonded to, the linking group that contains the carbon atoms that polar groups are not bonded to can make the polar group at the most terminal (terminal polar group) and the polar group that is adjacent to the terminal polar group be oriented so that they can adhere to protective layer.From this, it is estimated that when the carbon atoms that polar groups are bonded to each other are bonded through the linking group that contains the carbon atoms that polar groups are not bonded to, the lubricating layer that has high corrosion suppression effect for magnetic recording medium can be obtained.

[0032] On the other hand, when the fluorine-containing ether compound contained in the lubricating layer has an end group that the carbon atom that the polar group (terminal polar group) of the most terminal is bonded to and the carbon atom that the polar group that is adjacent to the terminal polar group is bonded to are bonded to, either of the polar groups among the terminal polar group and the polar group that is adjacent to the terminal polar group is oriented in the opposite direction to the protective layer.Therefore, either of the polar groups among the terminal polar group and the polar group that is adjacent to the terminal polar group is difficult to adhere to the protective layer, and the adhesion between the lubricating layer and the protective layer is poor.

[0033] R 1and R 7 In the case where the linking group between the carbon atom to which the terminal polar group is bonded and the carbon atom to which the polar group adjacent to the terminal polar group is bonded contains an oxygen atom (for example, in the case of a terminal group represented by the following formula (4-2), (4-3), or (4-4)), R 1 and R 7 The linking group preferably has a linear structure containing 2 to 5 carbon atoms to which no polar group is bonded. Even when the linking group contains an oxygen atom, if it has a linear structure containing 2 or more carbon atoms to which no polar group is bonded, the fluorine-containing ether compound will have good hydrophobicity. Furthermore, if the linking group has a linear structure containing 5 or less carbon atoms, the hydrophobicity of the linking group will not be too high, causing a problem in adhesion to the protective layer. In particular, if R 1 and R 7 When each of R has three polar groups, a lubricating layer with better adhesion to the protective layer can be formed. 1 and R 7 A lubricating layer containing a fluorine-containing ether compound in which the linking group has a linear structure containing the number of carbon atoms within the above range has excellent adhesion to the protective layer and, due to its appropriate hydrophobicity, can prevent the intrusion of water, resulting in a high corrosion-inhibiting effect on the magnetic recording medium. Also, R 1 and R 7 When the linking group has an oxygen atom, the linking group preferably has a linear structure consisting of 3 to 9 atoms, more preferably a linear structure consisting of 3 to 6 atoms. When the number of atoms contained in the linking group is within the above range, the molecular mobility is appropriate and intramolecular aggregation is less likely to occur. Therefore, the fluorine-containing ether compound can form a lubricating layer that has even better adhesion to the protective layer.

[0034] R 1 and R 7 In the case where the linking group between the carbon atom to which the terminal polar group is bonded and the carbon atom to which the polar group adjacent to the terminal polar group is bonded does not contain an oxygen atom (for example, in the case of a terminal group represented by the following formula (4-1) or (4-5)), R 1 and R 7In either case where the polar groups contained in R are two or three, the linking group preferably has a linear structure containing 1 to 4 carbon atoms to which no polar groups are bonded. When the linking group does not contain an oxygen atom and has a linear structure containing one or more carbon atoms to which no polar groups are bonded, the resulting fluorine-containing ether compound has good hydrophobicity. Furthermore, when the linking group has a linear structure containing four or fewer carbon atoms, the hydrophobicity of the linking group is not too high, which does not impair adhesion to the protective layer. Furthermore, since the linking group between the carbon atom to which the terminal polar group is bonded and the carbon atom to which the polar group adjacent to the terminal polar group is bonded does not contain an oxygen atom, intramolecular interaction is small and intramolecular aggregation is unlikely to occur. Therefore, the resulting fluorine-containing ether compound can form a lubricating layer with even better adhesion to the protective layer. As a result, R 1 and R 7 A lubricating layer containing a fluorine-containing ether compound in which the linking group has a linear structure containing the number of carbon atoms within the above range has excellent adhesion to the protective layer and, due to its appropriate hydrophobicity, can prevent the intrusion of water, resulting in a high corrosion-inhibiting effect on the magnetic recording medium.

[0035] In the fluorine-containing ether compound represented by formula (1), R 1 and R 7 may be the same or different, and are preferably the same. 1 and R 7 When R is the same, the fluorine-containing ether compound is likely to wet and spread evenly on the protective layer, and to easily obtain a lubricating layer having a uniform thickness. As a result, the lubricating layer containing this fluorine-containing ether compound has a good coverage, which is preferable. 1 and R 7 If the same, R 1 and R 7 In comparison with the case where the fluorine-containing ether compound is different, the fluorine-containing ether compound can be produced efficiently with fewer production steps.

[0036] In the fluorine-containing ether compound represented by formula (1), -R 1 and -R 7are each independently a terminal group represented by any one of the following formulas (4-1) to (4-5): 1 and -R 7 is a terminal group represented by any one of formulas (4-1) to (4-5), -R 1 and -R 7 contains two or three hydroxyl groups, and the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded has a linear structure containing the appropriate number of carbon atoms. 1 and -R 7 When is a terminal group represented by any of the formulae (4-1) to (4-5), the resulting fluorine-containing ether compound has appropriate hydrophobicity.

[0037] Additionally, -R 1 and -R 7 is an end group represented by any one of the following formulas (4-1), (4-2), (4-4), and (4-5), and contains three hydroxyl groups, the linking group between the carbon atom to which the hydroxyl group located on the perfluoropolyether chain is bonded and the carbon atom to which the hydroxyl group adjacent to that hydroxyl group is bonded also has a linear structure containing an appropriate number of carbon atoms. Therefore, the resulting fluorine-containing ether compound has better adhesion to the protective layer, appropriate hydrophobicity, and can form a lubricating layer with a high corrosion-inhibiting effect on magnetic recording media.

[0038] [ka] (In formula (4-1), e is an integer of 0 to 1, and f is an integer of 1 to 4.) (In formula (4-2), g is an integer of 1 to 2, and h is an integer of 1 to 3.) (In formula (4-3), i is an integer of 1 to 3.) (In formula (4-4), j is an integer of 1 or 2.)

[0039] In the terminal group represented by formula (4-1), e is an integer between 0 and 1, and f is an integer between 1 and 4. In the terminal group represented by formula (4-1), the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded does not contain an oxygen atom. Therefore, the terminal group exhibits appropriate hydrophobicity. Furthermore, since f is 4 or less, the linking group is not too hydrophobic, which would impair adhesion to the protective layer, and the terminal group exhibits excellent corrosion inhibition effect for magnetic recording media. Furthermore, since the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded does not contain an oxygen atom, the intramolecular interaction between the hydroxyl groups contained in the terminal group is small. Therefore, intramolecular aggregation is less likely to occur, and a lubricating layer with even better adhesion to the protective layer can be formed. Furthermore, when e is 1, the terminal group represented by formula (4-1) contains three hydroxyl groups, which results in better adhesion to the protective layer.

[0040] In the terminal group represented by formula (4-2), g is an integer of 1 to 2, and h is an integer of 1 to 3. Therefore, a fluorine-containing ether compound having a terminal group represented by formula (4-2) has good hydrophobicity and exhibits excellent corrosion inhibition effect for magnetic recording media. In the terminal group represented by formula (4-2), the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded contains an oxygen atom. In the terminal group represented by formula (4-2), h is 1 to 3, so the molecular mobility is appropriate. Therefore, intramolecular aggregation between the hydroxyl groups contained in the terminal group is unlikely to occur, resulting in even better adhesion to the protective layer. Furthermore, when g is 2, the terminal group represented by formula (4-2) contains three hydroxyl groups, so it exhibits even better adhesion to the protective layer.

[0041] In the terminal group represented by formula (4-3), i is an integer of 1 to 3. Therefore, a fluorine-containing ether compound containing a terminal group represented by formula (4-3) has good hydrophobicity and exhibits excellent corrosion inhibition effect for magnetic recording media. In the terminal group represented by formula (4-3), the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded contains an oxygen atom. In the terminal group represented by formula (4-3), i is 1 to 3, so that the molecular mobility is appropriate. Therefore, intramolecular aggregation between the hydroxyl groups contained in the terminal group is unlikely to occur, resulting in even better adhesion to the protective layer.

[0042] In the terminal group represented by formula (4-4), j is an integer of 1 to 2. Therefore, a fluorine-containing ether compound containing a terminal group represented by formula (4-4) has good hydrophobicity and exhibits excellent corrosion inhibition effect for magnetic recording media. The terminal group represented by formula (4-4) contains three hydroxyl groups, and therefore exhibits excellent adhesion to the protective layer.

[0043] The terminal group represented by formula (4-5) has good hydrophobicity because the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded does not contain an oxygen atom. Therefore, a lubricating layer containing a fluorine-containing ether compound having a terminal group represented by formula (4-5) exhibits excellent corrosion inhibition effect for magnetic recording media. Furthermore, since the terminal group represented by formula (4-5) contains three hydroxyl groups, it exhibits excellent adhesion to the protective layer.

[0044] (R 3 and R 5 ) In the fluorine-containing ether compound represented by formula (1), R 3 is a linking group represented by the following formula (2). The linking group represented by formula (2) is a group in which the oxygen atom in the parentheses on the right side of formula (2) is R 4 In the fluorine-containing ether compound represented by formula (1), R 5 is a linking group represented by the following formula (3). The linking group represented by formula (3) is a linking group in which the oxygen atom in the parentheses on the left side of formula (3) is R 4It is bonded to the adjacent methylene group (-CH2-).

[0045] [ka] (In formula (2), a is an integer of 1 to 3, and b is an integer of 1 or 2; in formula (3), c is an integer of 1 to 3, and d is an integer of 1 or 2; however, a in formula (2) and c in formula (3) cannot be 1 at the same time.)

[0046] In formula (2), a is an integer of 1 to 3, and in formula (3), c is an integer of 1 to 3. a in formula (2) and c in formula (3) cannot be 1 at the same time. That is, at least one of a and c is an integer of 2 to 3. Therefore, the fluorine-containing ether compound represented by formula (1) can be obtained by the reaction of R 3 In formula (2), a is 1, and R 5 In comparison with the compound in which c is 1 in formula (3), R 3 and / or R 5 The number of carbon atoms contained in the linking group represented by the formula (I) is large, and the hydrophobicity is good.

[0047] In the fluorine-containing ether compound represented by formula (1), it is preferable that a in formula (2) is an integer of 2 to 3, and c in formula (3) is an integer of 2 to 3. In this case, the hydrophobicity of the fluorine-containing ether compound represented by formula (1) is improved, and a lubricating layer containing this exhibits a more excellent corrosion-inhibiting effect on magnetic recording media.

[0048] In formula (2), b is an integer of 1 or 2, and in formula (3), d is an integer of 1 or 2. The hydroxyl groups in formulas (2) and (3) improve the adhesion of the lubricating layer containing a fluorinated ether compound to the protective layer. It is preferable that b in formula (2) and d in formula (3) are 1, since this results in a fluorinated ether compound that is easy to synthesize.

[0049] The fluorine-containing ether compound represented by formula (1) is R 3 is a linking group represented by formula (2), and R 5is a linking group represented by formula (3). 3 and R 5 The oxygen atoms at both ends of 3 and R 5 The four ether bonds thus formed give the fluorine-containing ether compound represented by formula (1) appropriate flexibility, and R 3 and R 5 This increases the affinity between the hydroxyl groups of the protective layer and the protective layer.

[0050] (R 2 , R 4 , R 6 ) In the fluorine-containing ether compound represented by formula (1), R 2 , R 4 , R 6 are the same or different perfluoropolyether chains (PFPE chains). 2 , R 4 , R 6 When a lubricant containing the fluorine-containing ether compound of this embodiment is applied to a protective layer to form a lubricating layer, the PFPE chains shown in Figure 1 coat the surface of the protective layer and impart lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer. Furthermore, the PFPE chains, due to their low surface energy, impart water resistance to the lubricating layer containing the fluorine-containing ether compound of this embodiment, thereby improving the corrosion resistance of a magnetic recording medium provided with a lubricating layer.

[0051] R 2 , R 4 , R 6 is a PFPE chain and can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound, etc. Examples of the PFPE chain include perfluoromethylene oxide polymer, perfluoroethylene oxide polymer, perfluoro-n-propylene oxide polymer, perfluoroisopropylene oxide polymer, and copolymers thereof.

[0052] The PFPE chain may be, for example, a structure represented by the following formula (Rf) derived from a polymer or copolymer of perfluoroalkylene oxide. -(CF2) w1 O(CF2O) w2 (CF2CF2O) w3 (CF2CF2CF2O) w4 (CF2CF2CF2CF2O) w5 (CF2) w6 - (Rf) (In formula (Rf), w2, w3, w4, and w5 represent an average degree of polymerization and each independently represent 0 to 20; provided that w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 represent an average value indicating the number of -CF2- and each independently represent 1 to 3; there are no particular limitations on the arrangement order of repeating units in formula (Rf).) In formula (Rf), w2, w3, w4, and w5 represent average degrees of polymerization, each independently representing 0 to 20, preferably 0 to 15, and more preferably 0 to 10. In formula (Rf), w1 and w6 are average values ​​indicating the number of -CF2- groups, and each independently represents 1 to 3. w1 and w6 are determined depending on the structure of the repeating units located at the ends of the chain structure in the polymer represented by formula (Rf), etc. In formula (Rf), (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) are repeating units. There are no particular restrictions on the arrangement order of the repeating units in formula (Rf). There are also no particular restrictions on the number of types of repeating units in formula (Rf).

[0053] R in Equation (1) 2 , R 4 , R 6 are each independently preferably a PFPE chain represented by the following formula (Rf-1): -(CF2) w7 O-(CF2CF2O) w8 -(CF2CF2CF2O) w9 -(CF2) w10 - (Rf-1) (In formula (Rf-1), w8 and w9 represent the average degree of polymerization, each independently representing 0.1 to 20; w7 and w10 represent the average value representing the number of -CF2-, each independently representing 1 to 2.) The sequence of the repeating units (CFCFO) and (CFCFCFO) in formula (Rf-1) is not particularly limited. Formula (Rf-1) may include any of a random copolymer, a block copolymer, and an alternating copolymer composed of the monomer units (CFCFO) and (CFCFCFO). In formula (Rf-1), w8 and w9, which represent the average degree of polymerization, each independently represent 0.1 to 20, preferably 0.1 to 15, and more preferably 1 to 10. In formula (Rf-1), w7 and w10 represent the average number of -CF- groups and each independently represent 1 to 2. w7 and w10 are determined depending on the structure of the repeating units located at the ends of the chain structure in the polymer represented by formula (Rf-1).

[0054] R in Equation (1) 2 , R 4 , R 6 are each preferably independently any one of the following formulas (5) to (9). The arrangement order of the repeating units (CFCFO) and (CFO) in formula (5) is not particularly limited. Formula (5) may include any of a random copolymer, a block copolymer, and an alternating copolymer composed of the monomer units (CF-CF-O) and (CF-O).

[0055] -CF2O-(CF2CF2O) k -(CF2O) l -CF2- (5) (In formula (5), k and l each represent an average degree of polymerization, and each represents 0.1 to 20.) -CF2O-(CF2CF2O) m -CF2- (6) (In formula (6), m represents the average degree of polymerization and represents 0.1 to 20.) -CF2CF2O-(CF2CF2CF2O) n -CF2CF2- (7) (In formula (7), n represents the average degree of polymerization and represents 0.1 to 20.) -CF2CF2CF2O-(CF2CF2CF2CF2O) o -CF2CF2CF2- (8) (In formula (8), o represents the average degree of polymerization and represents 0.1 to 10.) -CF(CF3)O-(CF2CF(CF3)O) p -CF(CF3)- (9) (In formula (9), p represents the average degree of polymerization and is 0.1 to 20.)

[0056] In formula (5), k and l each represent the average degree of polymerization and are 0.1 to 20; in formula (6), m represents the average degree of polymerization and is 0.1 to 20; in formula (7), n represents the average degree of polymerization and is 0.1 to 20; in formula (8), o represents the average degree of polymerization and is 0.1 to 10; and in formula (9), p represents the average degree of polymerization and is 0.1 to 20. k, l, m, n, o, and p can be selected arbitrarily within the above ranges. When k, l, m, n, o, and p are each 0.1 or greater, the resulting fluorine-containing ether compound provides a lubricating layer that can further inhibit corrosion of magnetic recording media. Furthermore, when k, l, m, n, and p are each 20 or less and o is 10 or less, the viscosity of the fluorine-containing ether compound does not become too high, making it easier to apply a lubricant containing the fluorine-containing ether compound, which is preferable. Each of k, l, m, n, o, and p, which indicate the average degree of polymerization, is preferably 1 to 10, more preferably 2 to 8, in order to provide a fluorinated ether compound that easily wets and spreads on a protective layer and easily forms a lubricating layer with a uniform thickness. Note that k, l, m, n, o, and p may be, for example, 0.5 to 9, 1 to 8, 2 to 7, 3 to 6, or 4 to 5.

[0057] R in Equation (1) 2 , R 4 , R 6 is any one of the formulas (5) to (9), the synthesis of the fluorine-containing ether compound is easy, which is preferable. 2 , R 4 , R 6is any one of formulas (5) to (7), it is more preferable because raw materials are easily available. Also, R 2 , R 4 , R 6 is any one of formulas (5) to (9), the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) to the number of carbon atoms in the perfluoropolyether chain is appropriate. This results in a fluorine-containing ether compound with appropriate hardness. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with sufficient coverage.

[0058] In the fluorine-containing ether compound represented by formula (1), R 2 , R 4 , R 6 The PFPE chains represented by may all be the same, may be different, or may only be partially the same. In this embodiment, the PFPE chains being the same also include cases where the PFPE chain structures (repeating units) are the same but the average degrees of polymerization are different. The fluorine-containing ether compound represented by formula (1) is easy to synthesize, so R 2 and R 6 It is preferable that R 2 and R 6 If the same, R 3 and R 5 is also the same, R 1 and R 7 It is more preferable that R 3 and R 5 are the same, the perfluoropolyether chain (R 4 ) for R 3 Atoms contained in and R 5 This means that the atoms in formula (2) are symmetrically arranged with respect to each other. In other words, this means that a in formula (2) is the same as c in formula (3), and b in formula (2) is the same as d in formula (3).

[0059] Specifically, the fluorine-containing ether compound represented by formula (1) is preferably any one of the compounds represented by the following formulae (A) to (T). In addition, ra, qb, sc, tc, rd, qe, qf, sg, tg, rh, qi, sj, tj, qk, rk, sl, tl, rl, qm, rm, qn, rn, qo, ro, qp, sp, tp, qq, sq, tq, sr, tr, rr, qs, ss, ts, st, tt, and rt in formulas (A) to (T) are values ​​indicating the average degree of polymerization, and are not necessarily integers.

[0060] The compounds represented by the following formulas (A) to (T) are all R 1 and R 7 is the same. The compounds represented by the following formulas (A) to (J) are all R 2 and R 4 and R 6 The compounds represented by the following formulae (K) to (T) are all R 2 and R 6 is the same.

[0061] The compounds represented by the following formulae (A) to (G), (K), (L), (N) to (P), (R), and (S) are all R 3 and R 5 are the same, a is 2 and b is 1 in formula (2), and c is 2 and d is 1 in formula (3). The compounds represented by the following formulas (H) to (J), (M), (Q), and (T) are all R 3 and R 5 are the same, a is 3 and b is 1 in formula (2), and c is 3 and d is 1 in formula (3).

[0062] The compound represented by the following formula (A) is R 1 and R 7 is a terminal group represented by formula (4-2), in which g is 1 and h is 2, and R 2 and R 4 and R 6 is the PFPE chain represented by formula (6). The compound represented by the following formula (B) is R 1 and R 7 is a terminal group represented by formula (4-2), in which g is 2, h is 2, and R 2 and R 4 and R 6 is the PFPE chain represented by formula (7). The compound represented by the following formula (C) is R 1 and R 7 is a terminal group represented by formula (4-1), in which e is 0, f is 1, and R 2 and R 4 and R 6 is the PFPE chain represented by formula (5).

[0063] The compound represented by the following formula (D) is R 1 and R 7 is a terminal group represented by formula (4-5), and R 2 and R 4 and R 6 is the PFPE chain represented by formula (6). The compound represented by the following formula (E) is R 1 and R 7 is a terminal group represented by formula (4-2), in which g is 1, h is 1, and R 2 and R 4 and R 6 is the PFPE chain represented by formula (7). The compound represented by the following formula (F) is R 1 and R 7 is a terminal group represented by formula (4-3), in which i is 1, and R 2 and R 4 and R 6 is the PFPE chain represented by formula (7).

[0064] The compound represented by the following formula (G) is R 1 and R 7 is a terminal group represented by formula (4-1), in which e is 1, f is 1, and R 2 and R 4 and R 6 is the PFPE chain represented by formula (5). The compound represented by the following formula (H) is R 1 and R 7 is a terminal group represented by formula (4-1), in which e is 0, f is 2, and R 2 and R 4 and R 6 is the PFPE chain represented by formula (6). The compound represented by the following formula (I) is R 1 and R 7 is a terminal group represented by formula (4-4), j in formula (4-4) is 2, and R 2 and R 4 and R 6 is the PFPE chain represented by formula (7).

[0065] The compound represented by the following formula (J) is R 1 and R 7 is a terminal group represented by formula (4-2), in which g is 2 and h is 1, and R 2 and R 4 and R 6 is the PFPE chain represented by formula (5). The compound represented by the following formula (K) is R 1 and R 7 is a terminal group represented by formula (4-1), in which e is 1, f is 1, and R 2 and R 6 is a PFPE chain represented by formula (7), and R 4 is the PFPE chain represented by formula (6). The compound represented by the following formula (L) is R 1 and R 7 is a terminal group represented by formula (4-4), j in formula (4-4) is 1, and R 2 and R 6 is a PFPE chain represented by formula (5), and R 4 is the PFPE chain represented by formula (6).

[0066] The compound represented by the following formula (M) is R 1 and R 7 is a terminal group represented by formula (4-2), in which g is 1 and h is 2, and R2 and R 6 is a PFPE chain represented by formula (7), and R 4 is the PFPE chain represented by formula (6). The compound represented by the following formula (N) is R 1 and R 7 is a terminal group represented by formula (4-2), in which g is 2, h is 2, and R 2 and R 6 is a PFPE chain represented by formula (6), and R 4 is the PFPE chain represented by formula (7). The compound represented by the following formula (O) is R 1 and R 7 is a terminal group represented by formula (4-5), and R 2 and R 6 is a PFPE chain represented by formula (6), and R 4 is the PFPE chain represented by formula (7).

[0067] The compound represented by the following formula (P) is R 1 and R 7 is a terminal group represented by formula (4-2), in which g is 1 and h is 3, and R 2 and R 6 is a PFPE chain represented by formula (5), and R 4 is the PFPE chain represented by formula (7). The compound represented by the following formula (Q) is R 1 and R 7 is a terminal group represented by formula (4-2), in which g is 1, h is 1, and R 2 and R 6 is a PFPE chain represented by formula (5), and R 4 is the PFPE chain represented by formula (7). The compound represented by the following formula (R) is R 1 and R 7 is a terminal group represented by formula (4-2), in which g is 2 and h is 1, and R 2 and R 6 is a PFPE chain represented by formula (6), and R 4 is the PFPE chain represented by formula (5).

[0068] The compound represented by the following formula (S) is R 1 and R 7 is a terminal group represented by formula (4-1), in which e is 0, f is 3, and R 2 and R 6 is a PFPE chain represented by formula (7), and R 4 is the PFPE chain represented by formula (5). The compound represented by the following formula (T) is R 1 and R 7 is a terminal group represented by formula (4-1), in which e is 1 and f is 2, and R 2 and R 6 is a PFPE chain represented by formula (6), and R 4 is the PFPE chain represented by formula (5).

[0069] [ka] (Fpa1 and Fpa2 in formula (A) are represented by formula (AF). In Fpa1 and Fpa2, ra represents the average degree of polymerization and represents 0.1 to 20. ra in Fpa1 and ra in Fpa2 may be the same or different.) (Fdb1 and Fdb2 in formula (B) are represented by formula (BF). In Fdb1 and Fdb2, qb represents the average degree of polymerization and represents 0.1 to 20. qb in Fdb1 and qb in Fdb2 may be the same or different.)

[0070] [ka] (Ffc1 and Ffc2 in formula (C) are represented by formula (CF). sc and tc in Ffc1 and Ffc2 represent the average degree of polymerization and represent 0.1 to 20. sc and tc in Ffc1 and sc and tc in Ffc2 may be the same or different.) (Fpd1 and Fpd2 in formula (D) are represented by formula (DF). In Fpd1 and Fpd2, rd represents the average degree of polymerization and represents 0.1 to 20. rd in Fpd1 and rd in Fpd2 may be the same or different.)

[0071] [ka] (Fde1 and Fde2 in formula (E) are represented by formula (EF). In Fde1 and Fde2, qe represents the average degree of polymerization and represents 0.1 to 20. qe in Fde1 and qe in Fde2 may be the same or different.) (Fdf1 and Fdf2 in formula (F) are represented by formula (FF). In Fdf1 and Fdf2, qf represents the average degree of polymerization and represents 0.1 to 20. qf in Fdf1 and qf in Fdf2 may be the same or different.)

[0072] [ka] (Ffg1 and Ffg2 in formula (G) are represented by formula (GF). sg and tg in Ffg1 and Ffg2 represent the average degree of polymerization and represent 0.1 to 20. sg and tg in Ffg1 and sg and tg in Ffg2 may be the same or different.) (Fph1 and Fph2 in formula (H) are represented by formula (HF). In Fph1 and Fph2, rh represents the average degree of polymerization and represents 0.1 to 20. rh in Fph1 and rh in Fph2 may be the same or different.)

[0073] [ka] (Fdi1 and Fdi2 in formula (I) are represented by formula (IF). In Fdi1 and Fdi2, qi represents the average degree of polymerization and represents 0.1 to 20. qi in Fdi1 and qi in Fdi2 may be the same or different.) (Ffj1 and Ffj2 in formula (J) are represented by formula (JF). sj and tj in Ffj1 and Ffj2 represent the average degree of polymerization, and represent 0.1 to 20. sj and tj in Ffj1 and sj and tj in Ffj2 may be the same or different.)

[0074] [ka] (Fdk1 and Fpk1 in formula (K) are represented by formula (KF). In Fdk1, qk represents the average degree of polymerization and is 0.1 to 20. In Fpk1, rk represents the average degree of polymerization and is 0.1 to 20.) (Ffl1 and Fpl1 in formula (L) are represented by formula (LF). In Ffl1, sl and tl represent the average degree of polymerization and represent 0.1 to 20. In Fpl1, rl represents the average degree of polymerization and represents 0.1 to 20.)

[0075] [ka] (Fdm1 and Fpm1 in formula (M) are represented by formula (MF). In Fdm1, qm represents the average degree of polymerization and is 0.1 to 20. In Fpm1, rm represents the average degree of polymerization and is 0.1 to 20.) (Fdn1 and Fpn1 in formula (N) are represented by formula (NF). In Fdn1, qn represents the average degree of polymerization and is 0.1 to 20. In Fpn1, rn represents the average degree of polymerization and is 0.1 to 20.)

[0076] [ka] (Fdo1 and Fpo1 in formula (O) are represented by formula (OF). In Fdo1, qo represents the average degree of polymerization and is 0.1 to 20. In Fpo1, ro represents the average degree of polymerization and is 0.1 to 20.) (Fdp1 and Ffp1 in formula (P) are represented by formula (PF). In Fdp1, qp represents the average degree of polymerization and is 0.1 to 20. In Ffp1, sp and tp represent the average degree of polymerization and are 0.1 to 20.)

[0077] [ka] (Fdq1 and Ffq1 in formula (Q) are represented by formula (QF). In Fdq1, qq represents the average degree of polymerization and is 0.1 to 20. In Ffq1, sq and tq represent the average degree of polymerization and is 0.1 to 20.) (Ffr1 and Fpr1 in formula (R) are represented by formula (RF). In Ffr1, sr and tr represent the average degree of polymerization and represent 0.1 to 20. In Fpr1, rr represents the average degree of polymerization and represents 0.1 to 20.)

[0078] [ka] (Fds1 and Ffs1 in formula (S) are represented by formula (SF). In Fds1, qs represents the average degree of polymerization and is 0.1 to 20. In Ffs1, ss and ts represent the average degree of polymerization and are 0.1 to 20.) (Fft1 and Fpt1 in formula (T) are represented by formula (TF). In Fft1, st and tt represent the average degree of polymerization and represent 0.1 to 20. In Fpt1, rt represents the average degree of polymerization and represents 0.1 to 20.)

[0079] If the compound represented by formula (1) is any of the compounds represented by the above formulas (A) to (T), the raw materials are easily available, and a lubricating layer that can suppress corrosion of the magnetic recording medium can be formed even if it is thin, which is preferable. When the compound represented by formula (1) is any of the compounds represented by formulas (B), (D), and (F) to (T), it is particularly preferable because a lubricating layer having a high corrosion suppression effect on the magnetic recording medium can be formed.

[0080] The fluorine-containing ether compound of this embodiment preferably has a number-average molecular weight (Mn) in the range of 500 to 10,000, more preferably in the range of 700 to 7,000, and particularly preferably in the range of 1,000 to 5,000. When the number-average molecular weight is 500 or more, the lubricant containing the fluorine-containing ether compound of this embodiment is less likely to evaporate, preventing the lubricant from evaporating and transferring to the magnetic head. Furthermore, when the number-average molecular weight is 10,000 or less, the viscosity of the fluorine-containing ether compound is appropriate, and a thin lubricating layer can be easily formed by applying a lubricant containing the compound. A number-average molecular weight of 5,000 or less is more preferred because it results in a manageable viscosity when applied to a lubricant.

[0081] The number average molecular weight (Mn) of fluorine-containing ether compounds was measured using AVANCEIII400 manufactured by Bruker Biospin. 1 H-NMR and 19 This is a value measured by F-NMR. In NMR (nuclear magnetic resonance) measurements, samples were diluted in a single or mixed solvent such as hexafluorobenzene, d-acetone, or d-tetrahydrofuran and used for the measurements. 19 The reference for F-NMR chemical shifts was set to −164.7 ppm for the hexafluorobenzene peak. 1 The reference for H-NMR chemical shifts was the acetone peak at 2.2 ppm.

[0082] "Manufacturing method" The method for producing the fluorinated ether compound of the present embodiment is not particularly limited, and the compound can be produced by a conventionally known production method. The fluorinated ether compound of the present embodiment can be produced, for example, by the production method shown below. In this embodiment, the fluorine-containing ether compound represented by formula (1) is 4 This will be explained by taking as an example the case of producing a compound having a symmetric structure with R at the center. 2 , R 4 , R 6 The three PFPE chains shown in R 1 and R7 is the same as R 3 and R 5 The following will explain the case of producing a compound in which

[0083] First, R in Equation (1) 4 A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain corresponding to the formula (I) is prepared. Next, the hydroxyl groups of the hydroxymethyl groups at both ends of the fluorine-based compound and the hydroxyl groups of the R 3 (=R 5 ) is reacted with a halogen compound having an epoxy group corresponding to R (first reaction). 4 At both ends of the perfluoropolyether chain corresponding to 3 (=R 5 ) to give intermediate compound 1 having an epoxy group corresponding to the above.

[0084] In producing the fluorine-containing ether compound of this embodiment, examples of the halogen compound having an epoxy group used in the first reaction include epichlorohydrin, epibromohydrin, 2-(2-bromoethyl)oxirane, 2-(2-chloroethyl)oxirane, 2-(3-bromopropyl)oxirane, and 2-(3-chloropropyl)oxirane. 3 a and / or R in formula (2) 5 When c in formula (3) is an integer of 2 to 3, examples of halogen compounds having an epoxy group include 2-(2-bromoethyl)oxirane, 2-(2-chloroethyl)oxirane, 2-(3-bromopropyl)oxirane, and 2-(3-chloropropyl)oxirane.

[0085] Next, R in formula (1) 2 (=R 4 =R 6A fluorine-based compound is prepared in which a hydroxymethyl group (-CHOH) is arranged at each end of a perfluoropolyether chain corresponding to R in formula (1). Then, the hydroxyl group of the hydroxymethyl group arranged at one end of the fluorine-based compound and the hydroxyl group of the hydroxymethyl group arranged at one end of the fluorine-based compound are combined. 1 (=R 7 ) (second reaction). 2 (=R 6 ) at one end of the perfluoropolyether chain corresponding to 1 (=R 7 ) to give intermediate compound 2 having a group corresponding to R 1 (=R 7 The epoxy compound having a group corresponding to the above formula (I) may be reacted with the above fluorine-based compound after protecting the hydroxyl group with an appropriate protecting group.

[0086] In producing the fluorinated ether compound of this embodiment, the epoxy compound used in the second reaction may be, for example, R 1 (or R 7 ) with a compound having an epoxy group selected from epichlorohydrin, epibromohydrin, 2-bromoethyloxirane, and allyl glycidyl ether. Such epoxy compounds may be synthesized by oxidizing an unsaturated bond, or may be purchased commercially.

[0087] Thereafter, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 2 is reacted with the epoxy groups located at both ends of the intermediate compound 1 (third reaction). By carrying out the above steps, R 2 , R 4 , R 6 The three PFPE chains shown in R 1 and R 7 is the same as R 3 and R 5Here, the order of the first reaction and the second reaction may be reversed.

[0088] Furthermore, for example, the fluorine-containing ether compound represented by formula (1) includes R 2 , R 4 , R 6 is the same, and R 3 and R 5 and R 1 and R 7 When a compound different from the above is to be produced, it can be produced by the production method shown below. That is, in the second reaction described above, R 1 and intermediate compound 2a having a group corresponding to R 7 Then, in the third reaction described above, intermediate compound 1 is synthesized with intermediate compound 2b having a group corresponding to R 3 (=R 5 ) can be produced by a method of reacting intermediate compound 2a and intermediate compound 2b in sequence with an epoxy group corresponding to

[0089] Furthermore, for example, the fluorine-containing ether compound represented by formula (1) includes R 2 , R 4 , R 6 is the same, and R 1 and R 7 and R 3 and R 5 When a compound different from the above is to be produced, it can be produced by the production method shown below. That is, in the first reaction described above, R 3 and a halogen compound having an epoxy group corresponding to R 5 Then, the resulting product is reacted with a halogen compound having an epoxy group corresponding to R 4 At one end of the perfluoropolyether chain corresponding to 3 and at the other end is an epoxy group corresponding to R 5Thereafter, intermediate compound 1a is used in place of intermediate compound 1 in the third reaction described above, whereby the compound can be produced.

[0090] Furthermore, for example, the fluorine-containing ether compound represented by formula (1) includes R 1 and R 7 is the same as R 3 and R 5 and R 2 and R 6 and two PFPE chains represented by R 4 When a compound having a different PFPE chain represented by the formula: is produced, it can be produced by the production method shown below. That is, in the first and second reactions described above, fluorine-based compounds having different types of PFPE chains are used, and apart from that, the production can be carried out by the same method as above.

[0091] Furthermore, for example, the fluorine-containing ether compound represented by formula (1) includes R 1 and R 7 and are the same or different, and R 3 and R 5 and R 2 , R 4 , R 6 When a compound having different PFPE chains represented by the formula: is produced, it can be produced by the production method shown below. That is, in the second reaction described above, two types of fluorine-based compounds are used, each having a different type of PFPE chain from the fluorine-based compound used in the first reaction. 2 R at one end of the perfluoropolyether chain corresponding to 1 and intermediate compound 2c having a group corresponding to R 6 R at one end of the perfluoropolyether chain corresponding to 7 Then, in the third reaction described above, intermediate compound 1 is synthesized by adding R 3 (=R 5) can be produced by reacting intermediate compound 2c and intermediate compound 2d in sequence with an epoxy group corresponding to the compound.

[0092] Here, the function of the lubricating layer formed on the protective layer using the lubricant containing the fluorine-containing ether compound of this embodiment will be described. One cause of corrosion of magnetic recording media is ionic contaminants present on the surface of the magnetic recording medium. Most ionic contaminants are externally attached during the manufacturing process of the magnetic recording medium. Ionic contaminants can also be generated when environmental substances that enter a hard disk drive (magnetic recording / reproducing device) adhere to the magnetic recording medium. Specifically, for example, when a magnetic recording medium and / or a hard disk drive are maintained under high temperature and humidity conditions, water containing environmental substances such as ions may adhere to the surface of the magnetic recording medium. When water containing environmental substances such as ions passes through the lubricating layer formed on the surface of the magnetic recording medium, it condenses minute ionic components present below the lubricating layer, generating ionic contaminants.

[0093] The fluorine-containing ether compound of this embodiment is a compound represented by formula (1), and therefore a lubricating layer containing this compound has a high corrosion-inhibiting effect that prevents contaminants from penetrating into the magnetic recording medium. This effect is achieved when the lubricating layer containing the fluorine-containing ether compound of this embodiment has the following properties: <1> ~ <5> By having the above functions, the adhesive layer has excellent adhesion to the protective layer, has appropriate hydrophobicity, and is easily formed on the protective layer in a uniform coating state, which is a synergistic effect.

[0094] <1> The lubricating layer is formed by the compound represented by formula (1) 3 and R 5 Each of R has one or more hydroxyl groups (-OH) and R 1 and R 7 The two or three polar groups contained in each of the lubricating layers create a favorable interaction with the protective layer, allowing the lubricating layer to adhere to the protective layer. As a result, the lubricating layer can prevent contaminants from penetrating into the magnetic recording medium, thereby suppressing corrosion of the magnetic recording medium.

[0095] <2> The fluorine-containing ether compound represented by formula (1) has three perfluoropolyether chains (R 2 , R 4 , R 6 ) but R 1 and R 3 Between R 3 and R 5 Between R 5 and R 7 are placed between them, respectively. For this reason, R 1 The polar group and R 3 The distance between the hydroxyl group and the 3 and R 5 The distance between the hydroxyl groups of 5 The hydroxyl group and R 7 The distance between the polar group and the R 3 and R 5 The hydroxyl group of R 1 and R 7 The polar groups of R are also less likely to be inhibited from bonding with the active sites on the protective layer by adjacent polar groups. 3 and R 5 The hydroxyl group of R 1 and R 7 The polar groups contained in the above fluorine-containing ether compound are all likely to be involved in bonding with the active sites on the protective layer. In other words, the polar groups contained in the above fluorine-containing ether compound are unlikely to become polar groups that are not involved in bonding with the active sites on the protective layer. As a result, the lubricating layer containing the above fluorine-containing ether compound has a reduced number of polar groups that are not involved in bonding with the active sites on the protective layer, and has excellent adhesion to the protective layer.

[0096] Also, R 3 The hydroxyl group and R 5 The distance between the hydroxyl group and the 1 The polar group and R 3 The distance between the hydroxyl group and the 5 The hydroxyl group and R 7 Since the distance between the polar groups of R 3 , R 5 , R 1 , R7 The intramolecular interaction between the polar groups in the fluorine-containing ether compound is small, and the compound is unlikely to aggregate. Therefore, the fluorine-containing ether compound represented by formula (1) can easily wet and spread on the protective layer, and can form a lubricating layer on the protective layer that has a uniform coating state, a high coverage rate, and good adhesion.

[0097] Furthermore, each perfluoropolyether chain (R 2 , R 4 , R 6 ) are at both ends of R 3 , R 5 , R 1 , R 7 The fluorine-containing ether compound is adhered to the protective layer by the polar group of either of the above. Therefore, the fluorine-containing ether compound applied to the protective layer is unlikely to be bulky. Therefore, the fluorine-containing ether compound represented by formula (1) can easily wet and spread on the protective layer, and can form a lubricating layer on the protective layer that has a uniform coating state, a high coverage rate, and good adhesion.

[0098] <3> The fluorine-containing ether compound represented by formula (1) has three perfluoropolyether chains (R 2 , R 4 , R 6 Each perfluoropolyether chain contained in the lubricating layer coats the surface of the protective layer, and also provides the lubricating layer with water resistance due to its low surface energy. The fluorine-containing ether compound represented by formula (1) contained in the lubricating layer undergoes thermal molecular motion when maintained under high temperature and humidity conditions. It is believed that water containing environmental substances such as ions penetrates through the gaps between the molecules in the lubricating layer. A lubricating layer containing a fluorine-containing ether compound represented by formula (1) has appropriate water resistance and hydrophobicity, and therefore prevents water from penetrating into the magnetic recording medium through gaps between molecules moving in the lubricating layer, thereby improving the corrosion resistance of the magnetic recording medium.

[0099] <4> In the fluorine-containing ether compound represented by formula (1), R 3 is a linking group represented by formula (2), and R 5is a linking group represented by formula (3), and a in formula (2) and c in formula (3) cannot simultaneously be 1. That is, the fluorine-containing ether compound represented by formula (1) is a fluorine-containing ether compound having a carbon atom bonded to a hydroxyl group in formula (2) and / or formula (3) and R 4 and a methylene chain having 2 or 3 carbon atoms between them. Therefore, the fluorine-containing ether compound represented by formula (1) has a lower molecular weight than the compound in which a in formula (2) is 1 and c in formula (3) is 1, because R 3 and / or R 5 The linking group represented by formula (1) contains a large number of carbon atoms, and has good hydrophobicity. As a result, a lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less permeable to water, and can prevent water from penetrating into the magnetic recording medium.

[0100] <5> In the fluorine-containing ether compound represented by formula (1), R 1 and R 7 Each polar group contained in R is bonded to a different carbon atom, and the carbon atoms bonded to the polar groups are bonded to each other via a linking group containing a carbon atom that is not bonded to a polar group. 1 and R 7 The carbon atom to which the polar group contained in R is bonded 1 and R 7 Due to the hydrophobicity of the carbon atoms contained in the linking group, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) has appropriate hydrophobicity. As a result, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is difficult for water to pass through, and can prevent water from penetrating into the magnetic recording medium, thereby suppressing corrosion of the magnetic recording medium.

[0101] [Lubricants for magnetic recording media] The lubricant for a magnetic recording medium of this embodiment contains a fluorine-containing ether compound represented by formula (1). The lubricant of the present embodiment can be used by mixing, as needed, known materials used as lubricant materials, as long as the properties resulting from the inclusion of the fluorinated ether compound represented by formula (1) are not impaired.

[0102] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco), etc. The known material to be mixed with the lubricant of the present embodiment preferably has a number average molecular weight of 1,000 to 10,000.

[0103] When the lubricant of this embodiment contains a material other than the fluorinated ether compound represented by formula (1), the content of the fluorinated ether compound represented by formula (1) in the lubricant of this embodiment is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 80% by mass or more, or 90% by mass or more.

[0104] The lubricant of this embodiment contains a fluorine-containing ether compound represented by formula (1), and therefore can form a lubricating layer that is highly effective in inhibiting corrosion of magnetic recording media. The lubricating layer made of the lubricant of this embodiment has a high corrosion-inhibiting effect on magnetic recording media, and therefore can be made thin.

[0105] [Magnetic recording media] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer provided in this order on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers may be provided between the substrate and the magnetic layer, if necessary. An adhesive layer and / or a soft magnetic layer may also be provided between the underlayer and the substrate.

[0106] FIG. 1 is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesive layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11.

[0107] "substrate" The substrate 11 may be, for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy. The substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or may be a non-magnetic substrate having a NiP or NiP alloy film formed on a base made of any of these non-metallic materials.

[0108] "Adhesion layer" The adhesive layer 12 prevents the progress of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are disposed in contact with each other. The material of the adhesive layer 12 can be appropriately selected from, for example, Cr, a Cr alloy, Ti, a Ti alloy, CrTi, NiAl, an AlRu alloy, etc. The adhesive layer 12 can be formed by, for example, a sputtering method.

[0109] "Soft magnetic layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the intermediate layer made of a Ru film is sandwiched between two soft magnetic films, and the soft magnetic films above and below the intermediate layer are antiferro-coupling (AFC).

[0110] The first and second soft magnetic films may be made of a material such as a CoZrTa alloy or a CoFe alloy. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used in the first and second soft magnetic films, which promotes the amorphization of the first and second soft magnetic films, improves the orientation of the first underlayer (seed layer), and reduces the flying height of the magnetic head. The soft magnetic layer 13 can be formed by, for example, a sputtering method.

[0111] "First base layer" The first underlayer 14 is a layer that controls the orientation and crystal size of the second underlayer 15 and magnetic layer 16 that are provided thereon. The first underlayer 14 may be, for example, a Cr layer, a Ta layer, a Ru layer, a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, or a CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0112] "Second base layer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a single layer or may be composed of multiple layers. When the second underlayer 15 is composed of multiple layers, all of the layers may be composed of the same material, or at least one layer may be composed of a different material. The second underlayer 15 can be formed by, for example, a sputtering method.

[0113] "Magnetic layer" The magnetic layer 16 is a magnetic film with an easy axis of magnetization oriented perpendicular or parallel to the substrate surface. The magnetic layer 16 contains Co and Pt, and may also contain oxides, Cr, B, Cu, Ta, Zr, or the like to further improve the SNR characteristics. Examples of oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, and TiO2.

[0114] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked in this order from the bottom, the first magnetic layer preferably has a granular structure made of a material containing Co, Cr, and Pt and further containing an oxide. The oxide contained in the first magnetic layer is preferably an oxide of Cr, Si, Ta, Al, Ti, Mg, Co, or the like. Among these, TiO2, Cr2O3, SiO2, and the like are particularly suitable. Furthermore, the first magnetic layer is preferably made of a composite oxide containing two or more types of oxides. Among these, Cr2O3-SiO2, Cr2O3-TiO2, SiO2-TiO2, and the like are particularly suitable.

[0115] The first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re in addition to Co, Cr, Pt, and oxides. The second magnetic layer can be made of the same material as the first magnetic layer, and preferably has a granular structure.

[0116] The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides, and may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt.

[0117] When magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When magnetic layer 16 is formed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0118] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can suitably be made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0119] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 preferably uses an alloy material containing an oxide, metal nitride, or metal carbide. Specifically, oxides that can be used include, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, and TiO2. Metal nitrides that can be used include, for example, AlN, Si3N4, TaN, and CrN. Metal carbides that can be used include, for example, TaC, BC, and SiC. The non-magnetic layer can be formed by, for example, a sputtering method.

[0120] To achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording, in which the axis of easy magnetization is oriented perpendicular to the substrate surface, but may also be a magnetic layer for longitudinal magnetic recording. The magnetic layer 16 may be formed by any conventionally known method such as vapor deposition, ion beam sputtering, magnetron sputtering, etc. The magnetic layer 16 is usually formed by sputtering.

[0121] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be made of a single layer or multiple layers. Examples of materials for the protective layer 17 include carbon, carbon containing nitrogen, and silicon carbide. A carbon-based protective layer, particularly an amorphous carbon protective layer, can be preferably used as the protective layer 17. When the protective layer 17 is a carbon-based protective layer, the interaction with the hydroxyl group contained in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced, which is preferable.

[0122] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrogenated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen content in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 to 20 atomic % when measured by hydrogen forward scattering (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 to 15 atomic % when measured by X-ray photoelectron spectroscopy (XPS).

[0123] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer, for example, in which nitrogen is contained on the lubricating layer 18 side of protective layer 17 and hydrogen is contained on the magnetic layer 16 side of protective layer 17. In this case, the adhesion between the magnetic layer 16 and lubricating layer 18 and the carbon-based protective layer is further improved.

[0124] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. If the thickness of the protective layer 17 is 1 nm or more, sufficient performance as the protective layer 17 can be obtained. If the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of making the protective layer 17 thinner.

[0125] The protective layer 17 can be formed by sputtering using a target material containing carbon, CVD (chemical vapor deposition) using a hydrocarbon raw material such as ethylene or toluene, or IBD (ion beam deposition). When a carbon-based protective layer is formed as protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when a carbon-based protective layer is formed as protective layer 17, it is preferable to deposit an amorphous carbon protective layer by plasma CVD. The amorphous carbon protective layer deposited by plasma CVD has a uniform surface with little roughness.

[0126] "Lubricating layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. The lubricating layer 18 also reduces the frictional force of the magnetic head of the magnetic recording / reproducing device that slides on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. 1, the lubricating layer 18 is formed on and in contact with the protective layer 17. The lubricating layer 18 contains the above-mentioned fluorine-containing ether compound.

[0127] When the protective layer 17 disposed below the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 bonds with the protective layer 17 with particularly high bonding strength. As a result, even if the thickness of the lubricating layer 18 is thin, it becomes easier to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high coverage, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0128] The average thickness of the lubricating layer 18 is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.0 nm (10 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming an island or mesh-like structure. This allows the lubricating layer 18 to cover the surface of the protective layer 17 with a high coverage. Furthermore, by setting the average thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be sufficiently reduced.

[0129] If the surface of the protective layer 17 is not covered with the lubricating layer 18 at a sufficiently high coverage rate, environmental substances adsorbed to the surface of the magnetic recording medium 10 will pass through the gaps in the lubricating layer 18 and penetrate underneath the lubricating layer 18. The environmental substances that penetrate underneath the lubricating layer 18 will adsorb and bond to the protective layer 17, generating contaminants. The generated contaminants (aggregated components) will adhere (transfer) to the magnetic head as smear during magnetic recording and playback, damaging the magnetic head or degrading the magnetic recording and playback characteristics of the magnetic recording and playback device.

[0130] Environmental substances that generate contaminants include, for example, siloxane compounds (cyclic siloxanes, linear siloxanes), ionic impurities, hydrocarbons with relatively high molecular weights such as octacosane, and plasticizers such as dioctyl phthalate. Examples of metal ions contained in ionic impurities include sodium ions and potassium ions. Examples of inorganic ions contained in ionic impurities include chloride ions, bromide ions, nitrate ions, sulfate ions, and ammonium ions. Examples of organic ions contained in ionic impurities include oxalate ions and formate ions.

[0131] "Method for forming lubricating layer" A method for forming the lubricating layer 18 includes, for example, preparing a magnetic recording medium in the middle of manufacturing in which the layers up to the protective layer 17 are formed on the substrate 11, applying a solution for forming the lubricating layer onto the protective layer 17, and drying the solution.

[0132] The lubricant layer forming solution can be obtained by dispersing and dissolving the lubricant for a magnetic recording medium according to the above embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the coating method. Examples of the solvent used in the lubricating layer-forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.).

[0133] The method for applying the lubricating layer-forming solution is not particularly limited, but examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, for example, the following method can be used. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in a lubricant layer-forming solution placed in an immersion tank of a dip coating device. Next, the substrate 11 is lifted from the immersion tank at a predetermined speed. In this way, the lubricant layer-forming solution is applied to the surface of the substrate 11 above the protective layer 17. By using the dipping method, the lubricating layer forming solution can be applied uniformly to the surface of the protective layer 17, and the lubricating layer 18 can be formed on the protective layer 17 with a uniform thickness.

[0134] In this embodiment, it is preferable to perform a burnishing (precision polishing) process after forming the lubricating layer 18 on the surface of the substrate 11. By performing the burnishing process, protruding defects and particles present on the surface of the substrate 11 on which the lubricating layer 18 has been formed can be removed, resulting in a magnetic recording medium 10 with a smooth surface. A smooth surface of the magnetic recording medium 10 can reduce spacing loss between the magnetic recording medium 10 and the magnetic head, improving signal characteristics. The burnishing step can be, for example, a step of scanning a burnishing tape over the surface of the substrate 11 on which the lubricating layer 18 has been formed. The burnishing tape can be, for example, a resin film holding abrasive grains. The grain size of the abrasive grains can be, for example, #6000 to #20000.

[0135] In this embodiment, it is preferable to perform a heat treatment on the substrate 11 on which the lubricating layer 18 is formed. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive force between the lubricating layer 18 and the protective layer 17 is also improved. The heat treatment temperature is preferably 100 to 180° C. If the heat treatment temperature is 100° C. or higher, the effect of improving the adhesion between the lubricating layer 18 and the protective layer 17 can be sufficiently obtained. Furthermore, by setting the heat treatment temperature to 180° C. or lower, thermal decomposition of the lubricating layer 18 can be prevented. The heat treatment time is preferably 10 to 120 minutes.

[0136] The magnetic recording medium 10 of this embodiment has at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18 sequentially formed on a substrate 11. In the magnetic recording medium 10 of this embodiment, a lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed on and in contact with the protective layer 17. This lubricating layer 18 is highly effective in suppressing corrosion of the magnetic recording medium 10. As a result, the magnetic recording medium 10 of this embodiment has few contaminants present on its surface, excellent corrosion resistance, and good reliability and durability. Furthermore, because the magnetic recording medium 10 of this embodiment has a lubricating layer 18 with a high corrosion suppression effect, the thickness of the protective layer 17 and / or the lubricating layer 18 can be reduced. Furthermore, the lubricating layer 18 in the magnetic recording medium 10 of this embodiment is less likely to produce foreign matter (smear), thereby suppressing pickup. [Example]

[0137] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0138] [Example 1] The compound represented by the above formula (A) was produced by the method shown below. (First reaction) Under a nitrogen gas atmosphere, place HOCH2CF2O (CF2CF2O) in a 200 mL recovery flask. r 9.4 g (20 mmol) of a compound (number average molecular weight 468, molecular weight distribution 1.1) represented by CF2CH2OH (where r, the average degree of polymerization, is 2.5), 1.76 g (44 mmol) of 60% sodium hydride, and 15.6 mL of N,N-dimethylformamide were charged and stirred at room temperature until homogeneous. 6.34 g (42 mmol) of 2-(2-bromoethyl)oxirane was added to this homogeneous solution and reacted with stirring at 40°C for 2 hours.

[0139] The reaction product obtained after the reaction was cooled to 25°C, and 80 mL of water was added to stop the reaction. The mixture was then transferred to a separatory funnel and extracted twice with 150 mL of ethyl acetate. The organic layer was washed with saturated brine and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.7 g (molecular weight 608, 6.0 mmol) of the compound represented by the following formula (10) as intermediate compound 1.

[0140] [ka] (In formula (10), r, which indicates the average degree of polymerization, is 2.5.)

[0141] (Second reaction) Under a nitrogen gas atmosphere, place HOCH2CF2O (CF2CF2O) in a 200 mL recovery flask. r 14.0 g of a compound (number average molecular weight 468, molecular weight distribution 1.1) represented by CF2CH2OH (where r, the average degree of polymerization, is 2.5), 3.89 g of a compound (molecular weight 216.28, 18 mmol) represented by the following formula (11), and 28 mL of t-butanol were charged and stirred at room temperature until homogeneous. 1.0 g of potassium tert-butoxide (molecular weight 112.2, 9 mmol) was further added to this homogeneous solution, and the mixture was reacted by stirring at 70°C for 16 hours.

[0142] The compound represented by formula (11) was synthesized by protecting one hydroxyl group of 1,3-propanediol with a THP group (tetrahydropyranyl group) and reacting the other hydroxyl group with epibromohydrin. The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 8.2 g (molecular weight 684, 12.0 mmol) of the compound represented by the following formula (12) as intermediate compound 2.

[0143] [ka] (In formula (11), THP represents a tetrahydropyranyl group.) (In formula (12), r, which indicates the average degree of polymerization, is 2.5.)

[0144] (Third reaction) Under a nitrogen gas atmosphere, 6.8 g of intermediate compound 2 represented by formula (12) (where r, the average degree of polymerization, is 2.5), 0.34 g of potassium tert-butoxide, and 9.4 mL of t-butanol were placed in a 200 mL recovery flask and stirred at room temperature until the mixture became homogeneous. 1.8 g of intermediate compound 1 represented by formula (10) (where r, the average degree of polymerization, is 2.5) was added to the homogeneous mixture and the mixture was allowed to react at 70°C for 16 hours with stirring.

[0145] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated using anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.3 g (molecular weight 1809, 1.8 mmol) of the compound represented by formula (A) above (Fpa1 and Fpa2 in formula (A) are represented by formula (AF). The average degree of polymerization (ra) in Fpa1 is 2.5, and the average degree of polymerization (ra) in Fpa2 is 2.5).

[0146] The obtained compound (A) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.38~1.75(8H), 3.37~4.31(46H) 19 F-NMR (CD3COCD3): δ[ppm]=-78.6(6F), -81.3(6F), -90.0~-88.5(30F)

[0147] [Example 2] In the first reaction, HOCH2CF2O(CF2CF2O) r Instead of the compound represented by CF2CH2OH (where r, which indicates the average degree of polymerization, is 2.5), HOCH2CF2CF2O(CF2CF2CF2O) q 13.9 g of a compound (number average molecular weight 693, molecular weight distribution 1.1) represented by CFCFCHOH (where q, which indicates the average degree of polymerization, is 2.5) was used, and in the second reaction, HOCHCFO(CFCFO) r Instead of the compound represented by CF2CH2OH (where r, which indicates the average degree of polymerization, is 2.5), HOCH2CF2CF2O(CF2CF2CF2O) q The same procedures as in Example 1 were carried out, except that 20.8 g of a compound (number average molecular weight 693, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where q, which indicates the average degree of polymerization, is 2.5) was used, and 6.02 g of a compound represented by the following formula (13) was used instead of the compound represented by formula (11), to obtain 4.7 g (molecular weight 2632, 1.8 mmol) of a compound represented by the above formula (B) (Fdb1 and Fdb2 in formula (B) are represented by formula (BF). qb, which indicates the average degree of polymerization in Fdb1, is 2.5, and qb, which indicates the average degree of polymerization in Fdb2, is 2.5).

[0148] The compound represented by formula (13) was synthesized by the following method. A TBS group (tert-butyldimethylsilyl group) was introduced to the primary hydroxyl group of 3-allyloxy-1,2-propanediol, and a MOM group (methoxymethyl group) was introduced to the secondary hydroxyl group of the resulting compound. After removing the TBS group from the resulting compound, the resulting primary hydroxyl group was reacted with 2-(chloropropoxy)tetrahydro-2H-pyran. The double bond of the resulting compound was oxidized. Through these steps, a compound represented by formula (13) was obtained.

[0149] [ka] (In formula (13), THP represents a tetrahydropyranyl group, and MOM represents a methoxymethyl group.)

[0150] The obtained compound (B) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.37~1.81(8H), 3.36~4.35(58H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(30F), -86.4(12F), -124.3(12F), -130.0~-129.0(15F)

[0151] [Example 3] In the first reaction, HOCH2CF2O(CF2CF2O) r Instead of the compound represented by CF2CH2OH (where r, which indicates the average degree of polymerization, is 2.5), HOCH2CF2O(CF2CF2O) s (CF2O) t 12.7 g of a compound (number average molecular weight 633, molecular weight distribution 1.1) represented by CF2CH2OH (where s and t, which indicate the average degree of polymerization, are 2.5) was used, and in the second reaction, HOCH2CF2O(CF2CF2O) r Instead of the compound represented by CF2CH2OH (where r, which indicates the average degree of polymerization, is 2.5), HOCH2CF2O(CF2CF2O) s (CF2O) t The same procedures as in Example 1 were carried out, except that 19.0 g of a compound (number average molecular weight 633, molecular weight distribution 1.1) represented by CF2CH2OH (in which s and t, which indicate the average degree of polymerization, are 2.5) was used, and 3.10 g of a compound represented by the following formula (14) was used instead of the compound represented by formula (11), to obtain 4.0 g (molecular weight 2216, 1.8 mmol) of a compound represented by the above formula (C) (Ffc1 and Ffc2 in formula (C) are represented by formula (CF). sc and tc, which indicate the average degree of polymerization in Ffc1, are 2.5, and sc and tc, which indicate the average degree of polymerization in Ffc2, are 2.5).

[0152] The compound represented by formula (14) was synthesized by introducing a THP group (tetrahydropyranyl group) into the primary hydroxyl group of 3-buten-1-ol and oxidizing the double bond of the resulting compound.

[0153] [ka] (In formula (14), THP represents a tetrahydropyranyl group.)

[0154] The obtained compound (C) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.67(8H), 3.39~4.34(38H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(15F), -77.7(6F), -80.3(6F), -91.0~-88.5(30F)

[0155] [Example 4] The same procedure as in Example 1 was carried out, except that 4.76 g of a compound represented by the following formula (15) was used instead of the compound represented by formula (11) in the second reaction, to obtain 3.4 g (molecular weight 1897, 1.8 mmol) of a compound represented by the above formula (D) (Fpd1 and Fpd2 in formula (D) are represented by formula (DF). The average degree of polymerization in Fpd1 is 2.5, and the average degree of polymerization in Fpd2 is 2.5).

[0156] The compound represented by formula (15) was synthesized by the following method. 1,2,4-butanetriol was reacted with benzaldehyde dimethyl acetal to synthesize a compound in which the hydroxyl groups bonded to the 2- and 4-carbon positions of 1,2,4-butanetriol were protected. This compound was reacted with 2-bromoethyloxirane to synthesize the compound represented by formula (15).

[0157] [ka] (In formula (15), Ph represents a phenyl group.)

[0158] The obtained compound (D) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.65(12H), 3.42~4.35(50H) 19 F-NMR (CD3COCD3): δ[ppm]=-78.6(6F), -81.3(6F), -90.0~-88.5(30F)

[0159] [Example 5] The same procedure as in Example 2 was carried out, except that 3.64 g of the compound represented by the following formula (16) was used instead of the compound represented by formula (13) in the second reaction, to obtain 4.4 g (molecular weight 2456, 1.8 mmol) of the compound represented by the above formula (E) (Fde1 and Fde2 in formula (E) are represented by formula (EF). qe, which indicates the average degree of polymerization in Fde1, is 2.5, and qe, which indicates the average degree of polymerization in Fde2, is 2.5).

[0160] The compound represented by formula (16) was synthesized by oxidizing a compound in which ethylene glycol monoallyl ether was protected with dihydropyran.

[0161] [ka] (In formula (16), THP represents a tetrahydropyranyl group.)

[0162] The obtained compound (E) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR(CD3COCD3):δ[ppm]=1.37~1.64(4H), 3.42~4.35(46H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(30F), -86.4(12F), -124.3(12F), -130.0~-129.0(15F)

[0163] [Example 6] The same procedure as in Example 2 was carried out, except that 3.89 g of a compound represented by the following formula (17) was used instead of the compound represented by formula (13) in the second reaction, to obtain 4.5 g (molecular weight 2484, 1.8 mmol) of a compound represented by the above formula (F) (Fdf1 and Fdf2 in formula (F) are represented by formula (FF). qf indicating the average degree of polymerization in Fdf1 is 2.5, and qf indicating the average degree of polymerization in Fdf2 is 2.5).

[0164] The compound represented by formula (17) was synthesized by reacting 3-buten-1-ol with 2-bromoethoxytetrahydropyran and oxidizing the double bond of the resulting compound.

[0165] [ka] (In formula (17), THP represents a tetrahydropyranyl group.)

[0166] The obtained compound (F) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.59(8H), 3.37~4.38(46H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(30F), -86.4(12F), -124.3(12F), -130.0~-129.0(15F)

[0167] [Example 7] The same procedure as in Example 3 was carried out, except that 4.51 g of a compound represented by the following formula (18) was used instead of the compound represented by formula (14) in the second reaction, to obtain 4.3 g (molecular weight 2364, 1.8 mmol) of a compound represented by the above formula (G) (Ffg1 and Ffg2 in formula (G) are represented by formula (GF). sg and tg, which represent the average degrees of polymerization in Ffg1, are 2.5, and sg and tg, which represent the average degrees of polymerization in Ffg2, are 2.5).

[0168] The compound represented by formula (18) was synthesized by the following method. 1,2,4-butanetriol was reacted with benzaldehyde dimethyl acetal to synthesize a compound in which the hydroxyl groups bonded to the 2- and 4-carbons of 1,2,4-butanetriol were protected. This compound was reacted with epibromohydrin to synthesize the compound represented by formula (18).

[0169] [ka] (In formula (18), Ph represents a phenyl group.)

[0170] The obtained compound (G) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.67(8H), 3.38~4.33(50H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(15F), -77.7(6F), -80.3(6F), -91.0~-88.5(30F)

[0171] [Example 8] The same procedures as in Example 1 were carried out, except that 2-(3-bromopropyl)oxirane was used instead of 2-(2-bromoethyl)oxirane in the first reaction, and 3.35 g of the compound represented by the following formula (19) was used instead of the compound represented by formula (11) in the second reaction, to obtain 3.2 g (molecular weight 1777, 1.8 mmol) of the compound represented by the above formula (H) (Fph1 and Fph2 in formula (H) are represented by formula (HF). rh, which indicates the average degree of polymerization in Fph1, is 2.5, and rh, which indicates the average degree of polymerization in Fph2, is 2.5).

[0172] The compound represented by formula (19) was synthesized by introducing a THP group (tetrahydropyranyl group) into the primary hydroxyl group of 4-penten-1-ol and oxidizing the double bond of the resulting compound.

[0173] [ka] (In formula (19), THP represents a tetrahydropyranyl group.)

[0174] The obtained compound (H) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.65(16H), 3.42~4.35(38H) 19 F-NMR (CD3COCD3): δ[ppm]=-78.6(6F), -81.3(6F), -90.0~-88.5(30F)

[0175] [Example 9] The same procedures as in Example 2 were carried out, except that 2-(3-bromopropyl)oxirane was used instead of 2-(2-bromoethyl)oxirane in the first reaction, and 6.99 g of the compound represented by the following formula (20) was used instead of the compound represented by formula (13) in the second reaction, to obtain 4.8 g (molecular weight 2688, 1.8 mmol) of the compound represented by the above formula (I) (Fdi1 and Fdi2 in formula (I) are represented by formula (IF). qi, which indicates the average degree of polymerization in Fdi1, is 2.5, and qi, which indicates the average degree of polymerization in Fdi2, is 2.5).

[0176] The compound represented by formula (20) was synthesized by the following method. A compound in which ethylene glycol monoallyl ether was protected with dihydropyran was oxidized to obtain Compound 1. Compound 1 was reacted with the hydroxyl group of 4-penten-1-ol to obtain Compound 2. The secondary hydroxyl group of Compound 2 was protected with a THP group, and the double bond was oxidized. Through these steps, a compound represented by formula (20) was obtained.

[0177] [ka] (In formula (20), THP represents a tetrahydropyranyl group.)

[0178] The obtained compound (I) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.38~1.58(16H), 3.38~4.41(58H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(30F), -86.4(12F), -124.3(12F), -130.0~-129.0(15F)

[0179] [Example 10] The same procedures as in Example 3 were carried out, except that 2-(3-bromopropyl)oxirane was used instead of 2-(2-bromoethyl)oxirane in the first reaction, and 5.77 g of the compound represented by the following formula (21) was used instead of the compound represented by formula (14) in the second reaction, to obtain 4.4 g (molecular weight 2452, 1.8 mmol) of the compound represented by the above formula (J) (Ffj1 and Ffj2 in formula (J) are represented by formula (JF). sj and tj, which indicate the average degree of polymerization in Ffj1, are 2.5, and sj and tj, which indicate the average degree of polymerization in Ffj2, are 2.5).

[0180] The compound represented by formula (21) was synthesized by the following method. A tert-butyldimethylsilyl (TBS) group was introduced as a protecting group to the primary hydroxyl group of 3-allyloxy-1,2-propanediol, and a methoxymethyl (MOM) group was introduced as a protecting group to the secondary hydroxyl group of the resulting compound. The TBS group was then removed from the compound, and the resulting primary hydroxyl group was reacted with 2-bromoethoxytetrahydropyran. The double bond of the resulting compound was then oxidized. The compound represented by formula (21) was obtained through these steps.

[0181] [ka] (In formula (21), THP represents a tetrahydropyranyl group, and MOM represents a methoxymethyl group.)

[0182] The obtained compound (J) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.66(8H), 3.39~4.35(58H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(15F), -77.7(6F), -80.3(6F), -91.0~-88.5(30F)

[0183] [Example 11] In the second reaction, HOCH2CF2O(CF2CF2O) r Instead of the compound represented by CF2CH2OH (where r, which indicates the average degree of polymerization, is 2.5), HOCH2CF2CF2O(CF2CF2CF2O) q The same procedures as in Example 1 were carried out, except that 20.8 g of a compound (number average molecular weight 693, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where q, which indicates the average degree of polymerization, is 2.5) was used, and 4.51 g of a compound represented by the above formula (18) was used instead of the compound represented by formula (11), to obtain 4.2 g (molecular weight 2319, 1.8 mmol) of a compound represented by the above formula (K) (Fdk1 and Fpk1 in formula (K) are represented by formula (KF). qk, which indicates the average degree of polymerization in Fdk1, is 2.5, and rk, which indicates the average degree of polymerization in Fpk1, is 2.5).

[0184] The obtained compound (K) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.63(8H), 3.39~4.35(50H) 19 F-NMR (CD3COCD3): δ[ppm]=-78.6(2F), -81.3(2F), -84.0~-83.0(20F), -86.4(8F), -90.0~-88.5(10F), -124.3(8F), -130.0~-129.0(10F)

[0185] [Example 12] In the second reaction, HOCH2CF2O(CF2CF2O) r Instead of the compound represented by CF2CH2OH (where r, which indicates the average degree of polymerization, is 2.5), HOCH2CF2O(CF2CF2O) s (CF2O) tThe same procedures as in Example 1 were carried out, except that a compound (number average molecular weight 633, molecular weight distribution 1.1) represented by CF2CH2OH (in which s and t, representing the average degree of polymerization, are 2.5) was used, and 6.02 g of a compound represented by the following formula (22) was used instead of the compound represented by formula (11). 4.1 g (molecular weight 2287, 1.8 mmol) of a compound represented by the above formula (L) (Ffl1 and Fpl1 in formula (L) are represented by formula (LF). sl and tl, representing the average degree of polymerization in Ffl1, are 2.5, and rl, representing the average degree of polymerization in Fpl1, is 2.5) was obtained.

[0186] The compound represented by formula (22) was synthesized by the following method. Ethylene glycol monoallyl ether was protected using dihydropyran, and the resulting compound was oxidized to obtain Compound 1. Compound 1 was then reacted with the hydroxyl group of 3-buten-1-ol to obtain Compound 2. The secondary hydroxyl group of the resulting Compound 2 was protected with a MOM group, and the double bond was oxidized to obtain a compound represented by formula (22).

[0187] [ka] (In formula (22), THP represents a tetrahydropyranyl group, and MOM represents a methoxymethyl group.)

[0188] The obtained compound (L) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.35~1.62(8H), 3.41~4.35(58H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -78.6(2F), -80.3(4F), -81.3(2F), -90.0~-88.5(30F)

[0189] [Example 13] In the second reaction, HOCH2CF2O(CF2CF2O) r Instead of the compound represented by CF2CH2OH (where r, which indicates the average degree of polymerization, is 2.5), HOCH2CF2CF2O(CF2CF2CF2O) q The same procedure as in Example 8 was carried out, except that 20.8 g of a compound (number average molecular weight 693, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where q, which indicates the average degree of polymerization, is 2.5) was used, and 3.89 g of a compound represented by the above formula (11) was used instead of the compound represented by formula (19), to obtain 4.1 g (molecular weight 2287, 1.8 mmol) of a compound represented by the above formula (M) (Fdm1 and Fpm1 in formula (M) are represented by formula (MF). qm, which indicates the average degree of polymerization in Fdm1, is 2.5, and rm, which indicates the average degree of polymerization in Fpm1, is 2.5).

[0190] The obtained compound (M) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.35~1.56(12H), 3.41~4.37(46H) 19 F-NMR (CD3COCD3): δ[ppm]=-78.6(2F), -81.3(2F), -84.0~-83.0(20F), -86.4(8F), -90.0~-88.5(10F), -124.3(8F), -130.0~-129.0(10F)

[0191] [Example 14] In the second reaction, HOCH2CF2CF2O(CF2CF2CF2O) q Instead of the compound represented by CFCFCHOH (where q, which indicates the average degree of polymerization, is 2.5), HOCHCFO(CFCFO) rThe same procedure as in Example 2 was carried out, except that 14.0 g of a compound (number average molecular weight 468, molecular weight distribution 1.1) represented by CF2CH2OH (in which r, indicating the average degree of polymerization, is 2.5) was used, to obtain 3.9 g (molecular weight 2182, 1.8 mmol) of a compound represented by the above formula (N) (Fdn1 and Fpn1 in formula (N) are represented by formula (NF). qn, indicating the average degree of polymerization in Fdn1, is 2.5, and rn, indicating the average degree of polymerization in Fpn1, is 2.5).

[0192] The obtained compound (N) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]=1.39~1.61(8H), 3.41~4.45(58H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -84.0~-83.0(10F), -86.4(4F), -90.0~-88.5(24F), -124.3(4F), -130.0~-129.0(5F)

[0193] [Example 15] The same procedure as in Example 14 was carried out, except that 4.76 g of the compound represented by the above formula (15) was used instead of the compound represented by the above formula (13) in the second reaction, to obtain 3.8 g (molecular weight 2122, 1.8 mmol) of the compound represented by the above formula (O) (Fdo1 and Fpo1 in formula (O) are represented by formula (OF). qo, which indicates the average degree of polymerization in Fdo1, is 2.5, and ro, which indicates the average degree of polymerization in Fpo1, is 2.5).

[0194] The obtained compound (O) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.58(12H), 3.38~4.41(50H) 19F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -84.0~-83.0(10F), -86.4(4F), -90.0~-88.5(24F), -124.3(4F), -130.0~-129.0(5F)

[0195] [Example 16] In the second reaction, HOCH2CF2CF2O(CF2CF2CF2O) q Instead of the compound represented by CFCFCHOH (where q, which indicates the average degree of polymerization, is 2.5), HOCHCFO(CFCFO) s (CF2O) t The same procedures as in Example 2 were carried out, except that a compound (number average molecular weight 633, molecular weight distribution 1.1) represented by CF2CH2OH (in which s and t, which indicate the average degree of polymerization, are 2.5) was used, and 4.15 g of a compound represented by the following formula (23) was used instead of the compound represented by the above formula (13), to obtain 4.3 g (molecular weight 2392, 1.8 mmol) of a compound represented by the above formula (P) (Fdp1 and Ffp1 in formula (P) are represented by formula (PF). qp, which indicates the average degree of polymerization in Fdp1, is 2.5. sp and tp, which indicate the average degree of polymerization in Ffp1, are 2.5).

[0196] The compound represented by formula (23) was synthesized by protecting one hydroxyl group of 1,4-butanediol with a THP group and reacting the other hydroxyl group with epibromohydrin.

[0197] [ka] (In formula (23), THP represents a tetrahydropyranyl group.)

[0198] The obtained compound (P) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR(CD3COCD3):δ[ppm]=1.37~1.61(12H), 3.40~4.43(46H) 19 F-NMR (acetone-D6): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -80.3(4F), -84.0 ~-83.0(10F), -86.4(4F), -91.0~-88.5(20F), -124.3(4F), -130.0~-129.0(5F)

[0199] [Example 17] In the second reaction, HOCH2CF2CF2O(CF2CF2CF2O) q Instead of the compound represented by CFCFCHOH (where q, which indicates the average degree of polymerization, is 2.5), HOCHCFO(CFCFO) s (CF2O) t The same procedures as in Example 9 were carried out, except that a compound (number average molecular weight 633, molecular weight distribution 1.1) represented by CF2CH2OH (where s and t, which indicate the average degree of polymerization, are 2.5) was used, and 3.64 g of a compound represented by formula (16) was used instead of the compound represented by formula (20) above. 4.3 g (molecular weight 2364, 1.8 mmol) of a compound represented by formula (Q) above (Fdq1 and Ffq1 in formula (Q) are represented by formula (QF). qq, which indicates the average degree of polymerization in Fdq1, is 2.5, and sq and tq, which indicate the average degree of polymerization in Ffq1, are 2.5) was obtained.

[0200] The obtained compound (Q) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.36~1.57(8H), 3.39~4.37(46H) 19F-NMR (acetone-D6): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -80.3(4F), -84.0 ~-83.0(10F), -86.4(4F), -91.0~-88.5(20F), -124.3(4F), -130.0~-129.0(5F)

[0201] [Example 18] In the second reaction, HOCH2CF2O(CF2CF2O) s (CF2O) t Instead of the compound represented by CF2CH2OH (where s and t, which indicate the average degree of polymerization, are 2.5), HOCH2CF2O(CF2CF2O) r The same procedures as in Example 3 were carried out, except that 14.0 g of a compound (number average molecular weight 468, molecular weight distribution 1.1) represented by CF2CH2OH (in which r, indicating the average degree of polymerization, is 2.5) was used, and 5.77 g of a compound represented by the above formula (21) was used instead of the compound represented by the above formula (14), to obtain 3.8 g (molecular weight 2094, 1.8 mmol) of a compound represented by the above formula (R) (Ffr1 and Fpr1 in formula (R) are represented by formula (RF). sr and tr, indicating the average degree of polymerization in Ffr1, are 2.5, and rr, indicating the average degree of polymerization in Fpr1, is 2.5).

[0202] The obtained compound (R) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]=1.34~1.59(4H), 3.40~4.43(58H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(5F), -77.7(2F), -78.6(4F), -80.3(2F), -81.3(4F), -90.0~-88.5(30F)

[0203] [Example 19] In the second reaction, HOCH2CF2O(CF2CF2O) s (CF2O)t Instead of the compound represented by CF2CH2OH (where s and t, which indicate the average degree of polymerization, are 2.5), HOCH2CF2CF2O(CF2CF2CF2O) q The same procedures as in Example 3 were carried out, except that 20.8 g of a compound (number average molecular weight 693, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where q, which indicates the average degree of polymerization, is 2.5) was used, and 3.61 g of a compound represented by the following formula (24) was used instead of the compound represented by the above formula (14), to obtain 4.3 g (molecular weight 2392, 1.8 mmol) of a compound represented by the above formula (S) (Fds1 and Ffs1 in formula (S) are represented by formula (SF). qs, which indicates the average degree of polymerization in Fds1, is 2.5, and ss and ts, which indicate the average degree of polymerization in Ffs1, are 2.5).

[0204] The compound represented by formula (24) was synthesized by introducing a THP group (tetrahydropyranyl group) into the primary hydroxyl group of 5-hexen-1-ol and oxidizing the double bond of the resulting compound.

[0205] [ka] (In formula (24), THP represents a tetrahydropyranyl group.)

[0206] The obtained compound (S) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.57(16H), 3.41~4.37(38H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(5F), -77.7(2F), -80.3(2F), -84.0~- 83.0(20F), -86.4(8F), -91.0~-88.5(10F), -124.3(8F), -130.0~-129.0(10F)

[0207] [Example 20] In the second reaction, HOCH2CF2O(CF2CF2O) s (CF2O) t Instead of the compound represented by CF2CH2OH (where s and t, which indicate the average degree of polymerization, are 2.5), HOCH2CF2O(CF2CF2O) r The same procedures as in Example 10 were carried out, except that a compound (number average molecular weight 468, molecular weight distribution 1.1) represented by CF2CH2OH (in which r, indicating the average degree of polymerization, is 2.5) was used, and 5.48 g of a compound represented by the following formula (25) was used instead of the compound represented by the above formula (21), to obtain 3.76 g (molecular weight 2090, 1.8 mmol) of a compound represented by the above formula (T) (Fft1 and Fpt1 in formula (T) are represented by formula (TF). st and tt, indicating the average degree of polymerization in Fft1, are 2.5, and rt, indicating the average degree of polymerization in Fpt1, is 2.5).

[0208] The compound represented by formula (25) was synthesized by the following method. The compound represented by formula (19) was reacted with allyl alcohol to obtain a compound in which the secondary hydroxyl group was protected with a MOM group. The double bond of the obtained compound was oxidized to obtain a compound represented by formula (25).

[0209] [ka] (In formula (25), THP represents a tetrahydropyranyl group, and MOM represents a methoxymethyl group.)

[0210] The obtained compound (T) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.35~1.60(16H), 3.42~4.42(50H) 19F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(5F), -77.7(2F), -78.6(4F), -80.3(2F), -81.3(4F), -90.0~-88.5(30F)

[0211] [Comparative Example 1] The compound represented by the following formula (AA) was synthesized by the method described in Patent Document 1.

[0212] [ka] (Fpaa1 and Ffaa1 in formula (AA) are represented by formula (AAF). paa, which indicates the average degree of polymerization in Fpaa1, is 2.5, and maa and naa, which indicate the average degrees of polymerization in Ffaa1, are both 2.5.)

[0213] The obtained compound (AA) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.42~4.28(38H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -78.6(2F), -80.3(4F), -81.3(2F), -90.0~-88.5(30F)

[0214] Comparative Example 2 The compound represented by the following formula (AB) was synthesized by the method described in Patent Document 1.

[0215] [ka] (Fpab1 and Ffab1 in formula (AB) are represented by formula (ABF). pab, which indicates the average degree of polymerization in Fpab1, is 2.5, and mab and nab, which indicate the average degree of polymerization in Ffab1, are both 2.5.)

[0216] The obtained compound (AB) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]=1.54~1.76(4H), 3.42~4.28(38H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -78.6(2F), -80.3(4F), -81.3(2F), -90.0~-88.5(30F)

[0217] Comparative Example 3 The compound represented by the following formula (AC) was synthesized by the method described in Patent Document 1.

[0218] [ka] (Fpac1 and Ffac1 in formula (AC) are represented by formula (ACF). pac, which indicates the average degree of polymerization in Fpac1, is 2.5, and mac and nac, which indicate the average degrees of polymerization in Ffac1, are both 2.5.)

[0219] The obtained compound (AC) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]=3.46~4.18(46H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -78.6(2F), -80.3(4F), -81.3(2F), -90.0~-88.5(30F)

[0220] Comparative Example 4 The compound represented by the following formula (AD) was synthesized by the method described in Patent Document 1.

[0221] [ka] (Fpad1 and Ffad1 in formula (AD) are represented by formula (ADF). pad, which indicates the average degree of polymerization in Fpad1, is 2.5, and mad and nad, which indicate the average degrees of polymerization in Ffad1, are both 2.5.)

[0222] The obtained compound (AD) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR (CD3COCD3): δ[ppm]=1.34~1.67(4H), 3.39~4.34(46H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -78.6(2F), -80.3(4F), -81.3(2F), -90.0~-88.5(30F)

[0223] Comparative Example 5 The compound represented by the following formula (AE) was synthesized by the method described in Patent Document 2.

[0224] [ka] (Fpae1 and Ffae1 in formula (AE) are represented by formula (AEF). pae, which indicates the average degree of polymerization in Fpae1, is 2.5, and mae and nae, which indicate the average degrees of polymerization in Ffae1, are each 2.5.)

[0225] The obtained compound (AE) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.65(8H), 3.42~4.35(46H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -78.6(2F), -80.3(4F), -81.3(2F), -90.0~-88.5(30F)

[0226] Comparative Example 6 The compound represented by the following formula (AF) was synthesized by the following method. The same operations as in Example 12 were carried out, except that epibromohydrin was used instead of 2-(2-bromoethyl)oxirane in the first reaction, and 4.47 g of a compound represented by the following formula (26) was used instead of the compound represented by formula (22) in the second reaction, to obtain 3.9 g (molecular weight 2143, 1.8 mmol) of a compound represented by the following formula (AF).

[0227] The compound represented by formula (26) was obtained by introducing THP groups as protecting groups into the primary and secondary hydroxyl groups of 3-allyloxy-1,2-propanediol and oxidizing the double bond of the resulting compound.

[0228] [ka] (In formula (26), THP represents a tetrahydropyranyl group.) (Fpaf1 and Ffaf1 in formula (AF) are represented by formula (AFF). paf, which indicates the average degree of polymerization in Fpaf1, is 2.5, and maf and naf, which indicate the average degree of polymerization in Ffaf1, are both 2.5.)

[0229] The obtained compound (AF) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.42~4.35(50H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -78.6(2F), -80.3(4F), -81.3(2F), -90.0~-88.5(30F)

[0230] Comparative Example 7 The compound represented by the following formula (AG) was synthesized by the method described in Patent Document 2.

[0231] [ka] (Fpag1 and Ffag1 in formula (AG) are represented by formula (AGF). pag, which indicates the average degree of polymerization in Fpag1, is 2.5, and mag and nag, which indicate the average degrees of polymerization in Ffag1, are both 2.5.)

[0232] The obtained compound (AG) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]=1.54~1.76(2H), 3.42~4.28(32H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(10F), -77.7(4F), -78.6(2F), -80.3(4F), -81.3(2F), -90.0~-88.5(30F)

[0233] [Comparative Example 8] The compound represented by the following formula (AH) was synthesized by the method described in Patent Document 1.

[0234] [ka] (Fpah1 and Ffah1 in formula (AH) are represented by formula (AHF). pah, which indicates the average degree of polymerization in Fpah1, ​​is 2.5, and mah and nah, which indicate the average degree of polymerization in Ffah1, are both 2.5.)

[0235] The obtained compound (AH) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]=3.42~4.28(38H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(5F), -77.7(2F), -78.6(4F), -80.3(2F), -81.3(4F), -90.0~-88.5(30F)

[0236] Comparative Example 9 The compound represented by the following formula (AI) was synthesized by the method described in Patent Document 1.

[0237] [ka] (Fpai1 and Fpai2 in formula (AI) are represented by formula (AIF). The pai representing the average degree of polymerization in Fpai1 is 2.5, and the pai representing the average degree of polymerization in Fpai2 is 2.5.)

[0238] The obtained compound (AI) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]=3.42~4.28(38H) 19 F-NMR (CD3COCD3): δ[ppm]=-78.6(6F), -81.3(6F), -90.0~-88.5(30F)

[0239] [Comparative Example 10] The compound represented by the following formula (AJ) was synthesized by the method described in Patent Document 1.

[0240] [ka] (Ffaj1 and Ffaj2 in formula (AJ) are represented by formula (AJF). maj and naj, which indicate the average degree of polymerization in Ffaj1, are 2.5, and maj and naj, which indicate the average degree of polymerization in Ffaj2, are 2.5.)

[0241] The obtained compound (AJ) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]=3.42~4.28(38H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(15F), -77.7(6F), -80.3(6F), -91.0~-88.5(30F)

[0242] [Comparative Example 11] The compound represented by the following formula (AK) was synthesized by the method described in Patent Document 2.

[0243] [ka] (Fpak1 and Fpak2 in formula (AK) are represented by formula (AKF). pak, which indicates the average degree of polymerization in Fpak1, is 2.5, and pak, which indicates the average degree of polymerization in Fpak2, is 2.5.)

[0244] The obtained compound (AK) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]= 1 H-NMR(CD3COCD3):δ[ppm]=3.46~4.18(46H) 19 F-NMR (CD3COCD3): δ[ppm]=-78.6(6F), -81.3(6F), -90.0~-88.5(30F)

[0245] [Comparative Example 12] The compound represented by the following formula (AL) was synthesized by the method described in Patent Document 2.

[0246] [ka] (Ffal1 and Ffal2 in formula (AL) are represented by formula (ALF). mal and nal, which indicate the average degree of polymerization in Ffal1, are 2.5, and mal and nal, which indicate the average degree of polymerization in Ffal2, are 2.5.)

[0247] The obtained compound (AL) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]= 1 H-NMR(CD3COCD3):δ[ppm]=3.46~4.18(46H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(15F), -77.7(6F), -80.3(6F), -91.0~-88.5(30F)

[0248] [Comparative Example 13] The compound represented by the following formula (AM) was synthesized by the method described in Patent Document 2.

[0249] [ka] (Fpam1 and Fpam2 in formula (AM) are represented by formula (AMF). pam, which indicates the average degree of polymerization in Fpam1, is 2.5, and pam, which indicates the average degree of polymerization in Fpam2, is 2.5.)

[0250] The obtained compound (AM) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. (Identification data) 1 H-NMR(CD3COCD3):δ[ppm]=3.46~4.18(32H) 19 F-NMR (CD3COCD3): δ[ppm]=-78.6(6F), -81.3(6F), -90.0~-88.5(30F)

[0251] [Comparative Example 14] The compound represented by the following formula (AN) was synthesized by the following method. Under a nitrogen gas atmosphere, place HOCH2CF2O (CF2CF2O) in a 200 mL recovery flask. r 14.0 g of a compound (number average molecular weight 468, molecular weight distribution 1.1) represented by CF2CH2OH (where r, the average degree of polymerization, is 2.5), 2.34 g of tert-butyl glycidyl ether (molecular weight 130.19, 18 mmol), and 28 mL of t-butanol were charged and stirred at room temperature until homogeneous. 1.0 g of potassium tert-butoxide (molecular weight 112.2, 9 mmol) was added to this homogeneous solution, and the mixture was stirred at 70°C for 16 hours to react.

[0252] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 7.2 g (molecular weight 598, 12.0 mmol) of the compound represented by the following formula (27).

[0253] [ka] (In formula (27), r, which indicates the average degree of polymerization, is 2.5.)

[0254] Under a nitrogen gas atmosphere, 7.2 g of the compound represented by formula (27) (where r, the average degree of polymerization, is 2.5), 0.67 g of potassium tert-butoxide, and 10.5 mL of t-butanol were placed in a 200 mL recovery flask and stirred at room temperature until homogeneous. 2.60 g of the compound represented by formula (28) below was added to this homogeneous solution, and the mixture was allowed to react at 70°C for 16 hours with stirring. The compound represented by formula (28) was synthesized by oxidation of diallyl ether.

[0255] [ka]

[0256] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 5.9 g (molecular weight 728, 7.7 mmol) of the compound represented by the following formula (29).

[0257] [ka] (In formula (29), r, which indicates the average degree of polymerization, is 2.5.)

[0258] Under a nitrogen gas atmosphere, 5.9 g of the compound represented by formula (29) (where r, the average degree of polymerization, is 2.5), 0.12 g of potassium tert-butoxide, and 2.8 mL of t-butanol were placed in a 200 mL recovery flask and stirred at room temperature until homogeneous. HOCH2CF2O(CF2CF2O) r1.6 g of a compound (number average molecular weight 468, molecular weight distribution 1.1) represented by CF2CH2OH (where r, which indicates the average degree of polymerization, is 2.5) was added, and the mixture was reacted at 70°C for 16 hours with stirring.

[0259] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.3 g (molecular weight 1812, 2.4 mmol) of the compound represented by the following formula (AN).

[0260] [ka] (Fpan1 and Fpan2 in formula (AN) are represented by formula (ANF). The value of pan representing the average degree of polymerization in Fpan1 is 2.5, and the value of pan representing the average degree of polymerization in Fpan2 is 2.5.)

[0261] The obtained compound (AN) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.47~4.24(50H) 19 F-NMR (CD3COCD3): δ[ppm]=-78.6(6F), -81.3(6F), -90.0~-88.5(30F)

[0262] The compounds of Examples 1 to 20 and Comparative Examples 1 to 14 thus obtained were applied to the formula (1) to obtain R 1 and R 7 (e and f in formula (4-1), g and h in formula (4-2), i in formula (4-3), j in formula (4-4), formula (4-5)), R 3 and R 5 (a and b in formula (2), c and d in formula (3)), R 2 , R4 , R 6 The structures (k and l in formula (5), m in formula (6), and n in formula (7)) are shown in Tables 1 and 2.

[0263] [Table 1]

[0264] [Table 2]

[0265] The number average molecular weights (Mn) of the compounds of Examples 1 to 20 and Comparative Examples 1 to 14 were calculated using the above-mentioned 1 H-NMR and 19 The average molecular weight of the synthesized compounds was determined by F-NMR measurement, and the results are shown in Table 3. It is estimated that there is a variation of about 1 to 5 in the average molecular weight of the synthesized compounds due to the molecular weight distribution of the fluoropolyether used as the raw material for the compounds and differences in the operations used to synthesize the compounds.

[0266] [Table 3]

[0267] Next, solutions for forming a lubricating layer were prepared by the method described below using the compounds obtained in Examples 1 to 20 and Comparative Examples 1 to 14. Then, using the obtained solutions for forming a lubricating layer, lubricating layers for magnetic recording media were formed by the method described below, thereby obtaining the magnetic recording media of Examples 1 to 20 and Comparative Examples 1 to 14.

[0268] "Lubricant layer forming solution" The compounds obtained in Examples 1 to 20 and Comparative Examples 1 to 14 were each dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.), and diluted with Vertrel XF so that the thickness of the coating film when applied to the protective layer would be 9 Å to 11 Å, to prepare a solution for forming a lubricating layer.

[0269] "Magnetic recording media" A magnetic recording medium was prepared by sequentially depositing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate with a diameter of 65 mm. The protective layer was made of carbon and had a thickness of 1 to 5 nm. On the protective layer of each magnetic recording medium on which the layers up to the protective layer had been formed, the lubricating layer-forming solutions of Examples 1 to 20 and Comparative Examples 1 to 14 were applied by dipping, with the dipping speed set to 10 mm / sec, the dipping time set to 30 sec, and the lifting speed set to 1.2 mm / sec.

[0270] Thereafter, a burnishing step was carried out in which a burnishing tape carrying abrasive grains of grain size #6000 was scanned over the surface of the magnetic recording medium on which the lubricating layer had been formed. The magnetic recording medium after the burnishing process was placed in a thermostatic chamber at 120° C. and subjected to a heat treatment in which it was heated for 10 minutes. By the above steps, magnetic recording media (with burnish) of Examples 1 to 20 and Comparative Examples 1 to 14 were obtained. Furthermore, magnetic recording media (without burnishing) of Examples 1 to 20 and Comparative Examples 1 to 14 were obtained in the same manner as the magnetic recording media with burnishing, except that the burnishing step was not carried out.

[0271] (film thickness measurement) The thickness of the lubricating layer of the magnetic recording media (with and without burnishing) obtained in this manner in Examples 1 to 20 and Comparative Examples 1 to 14 was measured using a Fourier transform infrared spectrophotometer (FT-IR) (product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). There was no difference in the thickness of the lubricating layer between the magnetic recording media with and without burnishing in any of Examples 1 to 20 and Comparative Examples 1 to 14. The results are shown in Table 3.

[0272] Next, the following corrosion resistance test was carried out on the magnetic recording media of Examples 1 to 20 and Comparative Examples 1 to 14, both with and without burnishing. (Corrosion resistance test) The magnetic recording media were exposed to conditions of 85°C and 90% relative humidity for 48 hours. After that, the number of corroded areas on the magnetic recording media was counted using an optical surface analyzer and evaluated based on the following criteria. The results are shown in Table 3.

[0273] "Evaluation Criteria" A: Less than 120 B: 120 or more, less than 150 C: 150 or more, less than 350 D: 350 or more, less than 1000 E: 1000 or more

[0274] As shown in Table 3, the magnetic recording media of Examples 1 to 20, which have a lubricating layer containing a compound represented by formula (1), showed good corrosion resistance in the corrosion resistance test results of A without tape varnish and A or B with tape varnish. In contrast, the magnetic recording media of Comparative Examples 1 to 14, both with and without tape varnish, showed results of C to E in the corrosion resistance test, and were inferior in corrosion resistance to the magnetic recording media of Examples 1 to 20.

[0275] More specifically, in the magnetic recording media of Examples 1 to 20, the lubricating layer is 3 is represented by formula (2) (where a is 2 and b is 1), and R 5 is represented by formula (3) (c is 2 and d is 1 in formula (3)), or R 3 is represented by formula (2) (where a is 3 and b is 1), and R 5 is the formula (3) (c is 3 and d is 1 in the formula (3)), and R 1 and R 7 is a terminal group represented by formulas (4-1) to (4-5). Therefore, the magnetic recording media of Examples 1 to 20 contain compounds in which R of the compounds in the lubricating layer is a terminal group represented by formulas (4-1) to (4-5). 3 and R 5 The number of carbon atoms contained in R is large, and the hydrophobicity is good. 1 and R 7 The carbon atom to which the polar group contained in R is bonded 1 and R7 The hydrophobicity of the carbon atoms contained in the linking group in R provides the lubricating layer with suitable hydrophobicity. 3 , R 5 , R 1 and R 7 The polar groups contained in each layer provide good adhesion to the protective layer. From these facts, it is presumed that the magnetic recording media of Examples 1 to 20 prevented water from entering the lubricating layer from the outside, thereby achieving good corrosion inhibition effects.

[0276] Furthermore, the magnetic recording media of Examples 8 to 10, 13, 17, and 20, both with and without burnish, received a result of A in the corrosion resistance test, demonstrating particularly excellent corrosion inhibition effects. This is because the lubricating layers of the magnetic recording media of Examples 8 to 10, 13, 17, and 20 have a R 3 is represented by formula (2) (where a is 3 and b is 1), and R 5 contains a compound represented by formula (3) (where c is 3 and d is 1), so R 3 and R 5 This is presumably because the number of carbon atoms contained in the polymer is greater (the methylene chain is longer), resulting in better hydrophobicity.

[0277] For example, R 1 and R 7 The terminal groups represented by R 3 and R 5 When magnetic recording media using compounds with different linking groups represented by the formula (Examples 1 and 13 vs. Comparative Example 4; Example 3 vs. Comparative Example 2; Examples 5 and 17 vs. Comparative Examples 3, 11, and 12; Example 16 vs. Comparative Example 5) were compared, R 3 and R 5 The more carbon atoms contained in the compound (the longer the methylene chain), the greater the corrosion inhibition effect.

[0278] Also, R 1 and R 7However, the magnetic recording media of Examples 3, 4, 7, 8, 11, 15, 19, and 20, in which the linking group between the carbon atom to which the terminal polar group is bonded and the carbon atom to which the polar group adjacent to the terminal polar group is bonded, was a terminal group represented by formula (4-1) or (4-5) that did not contain an ether bond (-O-), exhibited good corrosion inhibition effects. This is presumably because the linking group contained in the terminal group represented by formula (4-1) or (4-5) did not contain an ether bond and contained the appropriate number of carbon atoms, resulting in a lubricating layer with good hydrophobicity and preventing water penetration.

[0279] Also, R 1 and R 7 However, the magnetic recording media of Examples 1, 2, 5, 6, 9, 10, 12 to 14, and 16 to 18, in which the linking group between the carbon atom to which the terminal polar group is bonded and the carbon atom to which the polar group adjacent to the terminal polar group is bonded, is a terminal group represented by formula (4-2), (4-3), or (4-4) containing an ether bond, exhibited good corrosion inhibition effects. This is presumably because the linking group contained in the terminal group represented by formula (4-2), (4-3), or (4-4) contains an appropriate number of carbon atoms, resulting in a lubricating layer with good hydrophobicity and preventing water penetration.

[0280] Furthermore, R in formula (1) 1 and R 7 In Examples 2, 4, 7, 9 to 12, 14, 15, 18, and 20, each of which has three hydroxyl groups, the corrosion resistance test results were A both with and without burnish, and they showed particularly excellent corrosion inhibition effects. 1 and R 7 This is thought to be due to the three hydroxyl groups contained in each of the lubricating and protective layers exhibiting excellent adhesion to the protective layer. Excellent adhesion between the lubricating and protective layers prevents water from penetrating into the lubricating layer from the outside.

[0281] In contrast, in Comparative Example 6, R 1 and R 7Although each compound has three hydroxyl groups, the results of the corrosion resistance test were E (with burnish) and D (without burnish). This is because the compounds contained in the lubricating layer of the magnetic recording medium of Comparative Example 6 have R 3 is represented by formula (2) (where a is 1 and b is 1), and R 5 is the formula (3) (c is 1 and d is 1 in the formula (3)), and R 1 and R 7 This is presumably because the carbon atom bonded to the terminal hydroxyl group contained in the compound is bonded to the carbon atom bonded to the hydroxyl group adjacent to the terminal hydroxyl group. In a lubricating layer containing such a compound, either the terminal hydroxyl group or the hydroxyl group adjacent to the terminal hydroxyl group is oriented in the opposite direction relative to the protective layer, making it difficult to obtain adhesion of the hydroxyl group to the protective layer. In addition, a lubricating layer containing such a compound does not obtain sufficient hydrophobicity.

[0282] Furthermore, R in formula (1) 2 , R 4 , R 6 However, good corrosion resistance test results were obtained in Examples 1 to 10, which used any one PFPE chain selected from formula (5), formula (6), and formula (7), and in Examples 11 to 20, which used two types of PFPE chains selected from formula (5), formula (6), and formula (7).

[0283] Furthermore, R in formula (1) 3 is represented by formula (2) (where a is 1 and b is 1), and R 5 is the formula (3) (c is 1 and d is 1 in the formula (3)), and R 1 In Comparative Examples 7 and 13, where R is -OH, the results of the corrosion resistance test were both E. This is because the hydrophobicity of the lubricating layer was insufficient and, moreover, 1 This is presumably because the hydroxyl groups contained in the lubricating layer do not adhere well to the protective layer, resulting in a low coverage of the lubricating layer. [Industrial Applicability]

[0284] By using a lubricant for magnetic recording media containing the fluorine-containing ether compound of the present invention, a lubricating layer having a high corrosion-inhibiting effect on magnetic recording media can be formed. [Explanation of symbols]

[0285] 10...magnetic recording medium, 11...substrate, 12...adhesion layer, 13...soft magnetic layer, 14...first underlayer, 15...second underlayer, 16...magnetic layer, 17...protective layer, 18...lubricating layer.

Claims

1. A fluorine-containing ether compound represented by the following formula (1): R １ -CH ２ -R ２ -CH ２ -R ３ -CH ２ -R ４ -CH ２ -R ５ -CH ２ -R ６ -CH ２ -R ７ (1) (In formula (1), R ２ , R ４ and R ６ are the same or different perfluoropolyether chains; R ３ is a linking group represented by the following formula (2); R ５ is a linking group represented by the following formula (3); R １ and R ７ are each independently terminal groups containing two or three polar groups, each polar group being bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded being bonded via a linking group containing a carbon atom to which no polar group is bonded. All of the polar groups possessed by R 1 and R 7 are hydroxyl groups. 【Chemistry 1】 (In formula (2), a is an integer of 1 to 3, and b is an integer of 1 or 2; in formula (3), c is an integer of 1 to 3, and d is an integer of 1 or 2; however, a in formula (2) and c in formula (3) cannot be 1 at the same time.)

2. 2. The fluorine-containing ether compound according to claim 1, wherein a in said formula (2) is an integer of 2 or 3, and c in said formula (3) is an integer of 2 or 3.

3. In the formula (1), -R １ and -R ７ are each independently a terminal group represented by the following formulas (4-1) to (4-5): 【Chemistry 2】 (In formula (4-1), e is an integer of 0 to 1, and f is an integer of 1 to 4.) (In formula (4-2), g is an integer of 1 to 2, and h is an integer of 1 to 3.) (In formula (4-3), i is an integer of 1 to 3.) (In formula (4-4), j is an integer of 1 or 2.)

4. R in the formula (1) ２ , R ４ , R ６ 3. The fluorine-containing ether compound according to claim 1, wherein each of the following independently represents any one of the following formulas (5) to (9): -CF ２ O-(CF ２ CF ２ O) ｋ -(CF ２ O) ｌ -CF ２ - (5) (In formula (5), k and l each represent an average degree of polymerization, and each represents 0.1 to 20.) -CF ２ O-(CF ２ CF ２ O) ｍ -CF ２ - (6) (In formula (6), m represents the average degree of polymerization and is 0.1 to 20.) -CF ２ CF ２ O-(CF ２ CF ２ CF ２ O) ｎ -CF ２ CF ２ - (7) (In formula (7), n represents the average degree of polymerization and is 0.1 to 20.) -CF ２ CF ２ CF ２ O-(CF ２ CF ２ CF ２ CF ２ O) ｏ -CF ２ CF ２ CF ２ - (8) (In formula (8), o represents the average degree of polymerization and represents 0.1 to 10.) -CF(CF ３ )O-(CF ２ CF(CF ３ )O) ｐ -CF(CF ３ )- (9) (In formula (9), p represents the average degree of polymerization and is 0.1 to 20.)

5. In the formula (1), R １ and R ７ 3. The fluorine-containing ether compound according to claim 1, wherein:

6. In the formula (1), R ２ and R ６ 3. The fluorine-containing ether compound according to claim 1, wherein:

7. 3. The fluorine-containing ether compound according to claim 1, which has a number average molecular weight in the range of 500 to 10,000.

8. A lubricant for magnetic recording media, comprising the fluorine-containing ether compound according to claim 1 or 2.

9. A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, 3. A magnetic recording medium, wherein the lubricating layer comprises the fluorine-containing ether compound according to claim 1.

10. 10. The magnetic recording medium according to claim 9, wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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